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

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

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

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

Support a single directory traversal in RelativeLinkFilter

Prior, if we were viewing a blob at
`https://example.com/namespace/project/blob/master/doc/some-file.md` and
it contained a relative link such as `[README](../README.md)`, the
resulting link when viewing the blob would be:
`https://example.com/namespace/project/blob/README.md` which omits the
`master` ref, resulting in a 404.

Fixes https://gitlab.com/gitlab-org/release-tools/issues/3

See merge request !2247

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.

Help "SSH" fixes

A user was confused why ssh login did not work because he had used a nonstandard name during the key generation step. Maybe this will make it clearer.

See merge request !2296

Users must not change the default filename or they will have to create a
suitable .ssh/config which is out-of-scope here.

The keytype field is actually `ssh-dss` for DSA keys and they will not
be stored as `id_rsa.pub`.

Note that newer version of ssh actually also support
`ecdsa-sha2-nistp256` and others so it is also misleading to assume the
field always starts with `ssh-`.