Clean up overlap between dashboard and explore

- Clean up overlap between dashboard and explore. ... 5d785457
  - Split up SnippetsController into separate dashboard and explore sections.
  - Use consistent page titles, header titles and sidebars between dashboard and explore sections when signed in or not.
- Consistently case `Back to X` links. 260fcd45
- Link to help from signin page bottom. d92696d3
- Make Help accessible for guests. c258e977

cc @dzaporozhets

See merge request !1260

Syntax highlighting improvements

On the server side:

During development I would occasionally see SanitizationFilter sanitizing
the result of SyntaxHighlightFilter, even though its attributes were
whitelisted. This updates the `clean_spans` transformer to return the
whitelisted node as [suggested by the Sanitize docs](http://git.io/vZR8i).

On the client side:

- Makes the syntax_highlight JS more flexible
- Adds JS specs
- Simplifies highlighting of new notes
- Adds highlighting to Markdown preview

See merge request !1278

Add comments and clean up test for !1274

See merge request !1279

Bump rouge to 1.10.1 to remove warning noise and fix other syntax highlighting bugs

rouge warnings begone!

Closes #2128

Closes #2433

See merge request !1277

Also makes it work when given a parent element containing a
`.js-syntax-highlight` element so for dynamically-added things like
notes or Markdown previews, we can more accurately target just the
element we care about.

Closes #2128

Closes #2433

Fix some CHANGELOG entries

Noticed a few things were off.

See merge request !1276

Add missing 7.14.x CHANGELOG entries

[ci skip]

See merge request !1275

Gracefully handle errors in syntax highlighting by leaving the block unformatted

A bug in Rouge caused an Exception:

```undefined method `sub' for :Literal:Symbol```

That caused https://gitlab.com/embeddable-common-lisp/ecl/issues/156 to hit Error 500 and fail to display. If a failure occurs, just render the text as preformatted.

Closes #2433

See merge request !1274

Merge pull request #9604 from bpetheo/bpetheo_add_service_api_endpoint_to_retrive_service_parameters

Added service API endpoint to retrieve service parameters

Closes #2433

UI improvements

* Convert forked from button to text
* Refactor md variables
* Improve project fork page
* Style blob show page
* Style syntax highlight area for white theme

See merge request !1273

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Turned off autocomplete for new issue titles

See merge request !1271

Update OmniAuth test to pass in Semaphore

This has caused all the build failures on GitHub master for the last few days. This change seems to pass Semaphore build on GitHub:

https://semaphoreci.com/stanhu/gitlabhq/branches/fix-semaphore-twitter-identity-issue-try2

Closes #2469

See merge request !1272

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Fix 7.14 stable branch name in upgrade docs

[ci skip]

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Ui improvements

* allow containers without bg and border
* style twbs panels

See merge request !1270

Profile settings navigation improvements

* separate profile settings link
* get rid of double titles on profile page

See merge request !1269

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>