Add description of technical debt label in docs

Description for a technical debt label and workflow, as discussed in https://dev.gitlab.org/gitlab/organization/issues/714.

See merge request !3265

Make sure we get only two returns

@DouweM The other change I made which has nothing to do with Gitlab::Email::Receiver

See merge request !3360

Avoid using the same name between methods and variables

@DouweM This is the one with renaming.

See merge request !3359

Preserve time notes has been updated at when moving issue

Closes #14490

See merge request !3356

Fix build dependencies, when the dependency is a string

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/14485

See merge request !3344

Fix an issue causing the Dashboard/Milestones page to be blank

Fixes #14505 and #14514.

See merge request !3348

Fix sorting issues/mrs by votes on the groups page

Closes #14394 

The `non_archived` scope applied here https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/controllers/concerns/issues_action.rb#L5 overrides the previous `ORDER BY` applied inside the IssuesFinder, with the default scope of the Project model, resulting in SQL errors.

```ruby
Issue.reorder(created_at: :desc).joins(:project).to_sql
=> "SELECT issues.* 
    FROM issues INNER JOIN projects ON projects.id = issues.project_id
    ORDER BY issues.created_at DESC"

Issue.reorder(created_at: :desc).joins(:project).merge(Project.non_archived).to_sql
=> "SELECT issues.* 
    FROM issues INNER JOIN projects ON projects.id = issues.project_id 
    WHERE projects.archived = 'f'
    ORDER BY projects.id DESC"

Issue.reorder(created_at: :desc).joins(:project).merge(Project.non_archived.only(:where)).to_sql
=> "SELECT issues.* 
    FROM issues INNER JOIN projects ON projects.id = issues.project_id 
    WHERE projects.archived = 'f'
    ORDER BY issues.created_at DESC"
```

/cc @yorickpeterse 

See merge request !3333

Restrict notifications for confidential issues

Closes #14468 

/cc @rymai 

See merge request !3334

Moving of issuables only when the record already exists

Closes #14489

See merge request !3340

Fixes last remaining lints and enables scss-lint test for GitLab CI.

With this, builds will now fail if they break the SCSS style guide (at least, the parts enabled by the linter).

Discussed in #14299.

See merge request !3353

With this, builds will now fail if they break the SCSS style guide (at
least, the parts enabled by the linter).

Discussed in #14299.

Disabled SelectorFormat rule for SCSS Lint in order to get the Rake
task passing sooner.

SelectorFormat enforces that CSS classes and IDs use lowercase
hyphenated style, `like-this`, but a not-insignificant amount of
selectors in the codebase are `like_this`.

Fixing the selectors that break this rule would require changing HTML
as well, and potentially break JavaScript hooks, among other things. So
I decided to disable this rule for the time being, hopefully making it
easier to fix all the remaining warnings SCSS Lint is giving by removing
the most problematic rule.

Discussed in #14299.

See merge request !3309

Fixed bug where participants would not work correctly on merge requests

Also fixed alignment bug with can't merge badge

Closes #14478, #14494

See merge request !3329

Fixes issue with signin button overflowing on mobile

Closes #14477

![Screen_Shot_2016-03-22_at_13.52.51](/uploads/7c9b2c38be7d497c690a7d17ae0ca76d/Screen_Shot_2016-03-22_at_13.52.51.png)

![Screen_Shot_2016-03-22_at_13.52.43](/uploads/8b2432aeb4afec455286fced11c5490c/Screen_Shot_2016-03-22_at_13.52.43.png)

See merge request !3342

Auto collapses the navigation when resizing

Closes #14475 

![auto-collapse](/uploads/332c6261acb6bc30d7d30cbdfafe92eb/auto-collapse.gif)

See merge request !3343

Display nav controls on mobile

Set inputs inside .nav-controls to full-width on viewports below 600px

Fixes #13885

**Affected pages**


/dashboard/groups

/admin/builds

/dashboard/projects

/dashboard/issues

/dashboard/merge_requests

/dashboard/milestones

/dashboard/todos

/explore

/groups/{group-name}/issues

/groups/{group-name}

/groups/{group-name}/milestones

/{group-name}/{project-name}/builds

/{group-name}/{project-name}/forks

/{group-name}/{project-name}/issues

/{group-name}/{project-name}/labels

/{group-name}/{project-name}/merge_requests

/{group-name}/{project-name}/milestones

/{group-name}/{project-name}/wikis/home

/{group-name}/{project-name}/wikis/pages


Some Screenshots

**Groups**

![Screen_Shot_2016-03-15_at_2.22.23_PM](/uploads/b55348676693cc3ff67cddc4528f7f6c/Screen_Shot_2016-03-15_at_2.22.23_PM.png)


**Admin > Builds**

![admin-builds](/uploads/2e84119660f4895a1530883412c4b728/admin-builds.png)


**TODOs**

![todos](/uploads/84344c43011e22f902701038932d3eaa/todos.png)

**Dashboard > Projects**

![dashboards-projects](/uploads/f508d9107598038798aa10485d3d5cfe/dashboards-projects.png)


**Project Issues**

![issues](/uploads/d6c69a8f81ee07da95b2a3b99b81cf51/issues.png)


**Project Merge Requests**

![merge_requests](/uploads/b3c1a537f28931bd38077c36627a0d7a/merge_requests.png)


See merge request !3214

Shows error messages when trying to create label in dropdown menu

Closes #14495

![Screen_Shot_2016-03-22_at_14.46.10](/uploads/cdcaa51f4d41237f8027efbd0f894bcd/Screen_Shot_2016-03-22_at_14.46.10.png)

See merge request !3345

Fixes issue with assign milestone not loading milestone list

cc. @jschatz1 

See merge request !3346

Grafana installation and configuration documentation

Adding documentation for installing and configuring Grafana. This also includes providing dashboards users can import.

Fixes gitlab-org/omnibus-gitlab#1008

cc/ @axil

See merge request !3015

Reload the schema before restoring a database backup

If a user tries to downgrade and restore after a failed upgrade,
the database may still contain newer tables. Reload the older
schema before restoring the database to avoid future upgrade
problems. Also, add a rake task to help users add migration
versions to the database so it's easier to recover from these
errors if they do occur. Fixes #13419

See merge request !2807

User has to confirm deletion of issuables

Closes #14474

See merge request !3341

Closes #14495

[ci skip]