Define a limited set of filters for SingleLinePipeline

Removes the following filters from its parent GfmPipeline:

- SyntaxHighlightFilter
- UploadLinkFilter
- TableOfContentsFilter
- LabelReferenceFilter
- TaskListFilter

Closes #1697 

See merge request !2257

Fix mentionable reference extraction caching.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/4130

Reverts https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/2120 and https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/2283

See merge request !2315

See merge request !2316

Enable Microsoft Azure OAuth2 support

Added Microsoft Azure as OAuth2 provider (https://github.com/KonaTeam/omniauth-azure-oauth2) including docs and icon.

See merge request !2187

Transaction timings are also already stored in milliseconds, this keeps
things consistent.

Fix project destroy callback

See gitlab-org/gitlab-ee!107.

See merge request !2307

Import GitHub Pull Requests into GitLab

Fixes #2833

See merge request !2168

This reverts commit d337d5e7.

This reverts commit 4b027bc9.

Fix notification spec

Master was broken :(

See merge request !2306

Fix the abuse report detail URL in the HTML email template

Previous URL resulted in a 404.

See merge request !2310

Ignore config/sidekiq.yml

Removes the following filters from its parent GfmPipeline:

- SyntaxHighlightFilter
- UploadLinkFilter
- TableOfContentsFilter
- LabelReferenceFilter
- TaskListFilter

Closes #1697

Validate README format

Take the first previewable README file as project's README, otherwise if
none file is available, or we can't preview any of them, we assume that
project doesn't have a README file.

Fixes #3978

Update version check images to use SVG

See merge request !2244

See gitlab-org/gitlab-ee!107.

Better support for referencing and closing issues in asana_service.rb (by @mikew1)



See merge request !2302

Add graphs of commits ahead/behind default branch (by @brunsa2)

Replaces https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/1716

See merge request !2301

Show 'New Merge Request' buttons on canonical repo. (by @joshfng)

Replaces https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/2189 to run tests on our runners.

See merge request !2300

Abuse Report refactors

- Redirect back to user profile after report
- "Tell, Don't Ask" for sending report notifications

See merge request !2293

Merge pull request GH-9938 from huacnlee/hotfix/note_mail_with_notification

Hotfix note mail with notification

See merge request !2288