Ui improvements

* improve UI for commits, issues and merge requests lists
* refactor commit css

See merge request !1550

Ui improvements

* update bootstrap
* move milestones and labels to the left
* make open/closed/all filter as tab
* make issues page more compact

For  #1871

See merge request !1549

Correctly set default projects limit for new users.

See #2014.

Note that the projects limit still isn't retroactively applied to existing users (probably as intended)

See merge request !1547

Add missing color codes for line anchors, fixes #8628

Document fun facts about omnibus-gitlab

I hope this helps developers understand some of the differences.

See merge request !1546

Revert upload refactor

See merge request !1548

This reverts commit 7d5f86f6.

This reverts commit ebd39fc0.

Update API branches documentation [ci skip]

Structure oauth docs

Fixes #2010

@valery please let me know if I used the right terminology (GitLab as an OAuth2 client)

See merge request !1545

Fix push access check when not signed in.

Was causing 500 on MR, Blob, Tree pages.

Fixes https://github.com/gitlabhq/gitlabhq/issues/8637 and https://github.com/gitlabhq/gitlabhq/issues/8813.

See merge request !1542

Fix user page performance

See merge request !1543