Code improvements, bug fixes, finish documentation and specs

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Before:   
![Screen_Shot_2016-10-24_at_2.43.09_PM](/uploads/5543b6e134a5349650b24dcb1b1a9082/Screen_Shot_2016-10-24_at_2.43.09_PM.png)

After:   
![Screen_Shot_2016-10-24_at_2.42.55_PM](/uploads/a561c8708ca2b17d11c0eb9b2cfd0b9b/Screen_Shot_2016-10-24_at_2.42.55_PM.png)

Closes #23607

See merge request !7079

Add ESLint

## What does this MR do?

- create `package.json`
- add ESLint dependencies to `package.json`
- add JavaScript linting to CI
- add Rake task `lint:javascript`as alias for `eslint` (which itself is an alias for `npm run eslint`)

## Are there points in the code the reviewer needs to double check?

Probably not.

## Why was this MR needed?

My hovercraft was full of eels.

## What are the relevant issue numbers?

- https://gitlab.com/gitlab-org/gitlab-ce/issues/13224#note_12537431
- https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5006#note_13255658


See merge request !5445

Resolve "Lacking padding on syntax highlight blocks in diff comments"

## What does this MR do?

Enforces horizontal padding on highlight block.

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

There was no horizontal padding on diff comment highlight blocks.

## Screenshots (if relevant)

![Screen_Shot_2016-10-23_at_01.48.10](/uploads/6d7a426c0856e8787b63b2c02672298a/Screen_Shot_2016-10-23_at_01.48.10.png)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?


Closes #23661

See merge request !7062

Refactored less readable existance checks

## What does this MR do?
Clean up complex JavaScript expressions generated by conditional assignment and existence checks in CoffeeScript.
These are small changes that effect 1 or 2 lines at a time, but should make sections of code more readable.

## Are there points in the code the reviewer needs to double check?
Changes in [gl_dropdown.js](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/assets/javascripts/gl_dropdown.js) don't do much (largely just splitting stuff onto multiple lines). Is this a bit pointless?

## Why was this MR needed?
Auto-generated JS contains complex expressions that will be difficult to work with in future.

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

A child issue of #21887 
Closes #21988

See merge request !6289

Add all endoints to JIRA service API documentation

## What does this MR do?

Add missing API endpoints to the JIRA service.

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ee/issues/440

See merge request !7122

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/440

We don't need to run `ee_compat_check` against `master`

See merge request !7119

Add a trigger variable to docs trigger job

See merge request !7089

CoffeeScript generated JavaScript contains some unreadable
expressions. This refactoring addresses complex uses of
the exestential operator that produced unreadable Javascript.

See merge request !7086

Changed .visable-sm to .visible-sm

Fixes #23745
Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

Issue board sidebar

## What does this MR do?

Adds a sidebar when clicking an issue in the issue boards lists. This allows user to easily update other parts of the issue details without having to visit the issue itself. Same functionality as on issue page.

When creating a new issue the sidebar automatically opens.

## Screenshots (if relevant)

![Screen_Shot_2016-10-07_at_13.10.16](/uploads/ad08785f407d8ac3fe9cb078868a7839/Screen_Shot_2016-10-07_at_13.10.16.png)

## What are the relevant issue numbers?

Closes #21219

See merge request !6690

Fix refs dropdown selection with special characters

## What does this MR do?

Remove unneeded encode from the project-refs-dropdown renderRow method.

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

## Screenshots (if relevant)

![2016-10-23_01.20.19](/uploads/1f176b2aa633093851799ae9f70f116b/2016-10-23_01.20.19.gif)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?


Closes #21248

See merge request !7061

Fix Sidekiq process stats in admin area

Closes #23825

See merge request !7116

Fix filtering of milestones with quotes in title

Closes #23268

See merge request !6900

users should remove former Go installation folder

## What does this MR do?

It ensure users installing or updating from source will remove their former Go installation folder in `/usr/local/go`, to avoid raising errors that could lead to new issues being created.

## Are there points in the code the reviewer needs to double check?

1. The `rm -rf` should not be verbose if folder does not exists.
1. May a user have some kind of configuration files in this folder ?

## Why was this MR needed?

I did faced the error, that led me to the solution stated here : https://gitlab.com/gitlab-org/gitlab-workhorse/issues/29#note_4155517

gitlab-org/gitlab-workhorse#29

See merge request !6602

See merge request !6784

When adding a deploy key that already exists in the project the existing key would not be returned, resulting in an attempt to create a new one, which in turn caused a 500 error due to an ActiveRecord exception.

When adding a deploy key that exists within another project the key would be joined to the project, but would also attempt to create a new one, which resulted in a 400 error due to the key already existing.

Fixes #22741
Fixes #21754
Signed-off-by: Rémy Coutable <remy@rymai.me>

See merge request !6915

Signed-off-by: Rémy Coutable <remy@rymai.me>

Grapify tags API

## What does this MR do?

Add the Grape-DSL to the tags API.

## Are there points in the code the reviewer needs to double check?

The delete endpoint only has a description but no success entity because we don't have one. We only return the branch name as JSON. Should I do something else?

## What are the relevant issue numbers?

Related to #22928

See merge request !6860

Signed-off-by: Rémy Coutable <remy@rymai.me>

ESLint config: https://github.com/airbnb/javascript

Remove use of wait_for_ajax since jQuery was removed

Fixes #23812

See merge request !7111

Replace jquery-cookie plugin with js-cookie

## What does this MR do?

Removes an outdated and unmaintained dependency [jquery.cookie](https://github.com/carhartl/jquery-cookie) with its successor [js.cookie](https://github.com/js-cookie/js-cookie) which is not dependent on jQuery.

Also this MR adds a global default cookie `path` setting which defaults to the GitLab root directory.  Now, setting a cookie to any path other than `gon.relative_url_root` requires an explicit opt-out.  This is a sensible default and should prevent accidental omission going forward.

## Are there points in the code the reviewer needs to double check?

Double check that all instances of `$.cookie(x)` have been replaced by `Cookies.get(x)` and all instances of `$.cookie(x, y, z)` are replaced with `Cookies.set(x, y, z)`.  All javascripts which set or retrieve cookie values should function just as before.

## Why was this MR needed?

One more step toward shaking off jQuery as a dependency (#23022), also [jquery.cookie](https://github.com/carhartl/jquery-cookie) is no longer maintained and hasn't seen an update in 2+ years.

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) entry added
- Tests
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

#23022

See merge request !7085

Fixes #23812

Specify which Fog storage drivers are imported by default in backup_restore.md

Replaces https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5783

See merge request !7108