Fix and test leave project display

The 'Leave this project' display on project page was broken. It was calling the method incorrectly, which returned `nil` and displayed nothing. 

This fixes the display and also adds 2 different tests for it.

cc/ @jvanbaarsen @stanhu Please review and merge if you think it looks good. Thank you!

See merge request !2166

New group page

Implementing from https://gitlab.com/gitlab-org/gitlab-ce/issues/3480#note_2722988

cc @skyruler 

For https://gitlab.com/gitlab-org/gitlab-ce/issues/3480

See merge request !2174

Hotfix for sidekiq-cron being loaded from Settingslogic with defaults

This fixes a regression with "Stack level too deep" from master.

See merge request !2173

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

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

New colour scheme

old
![Screenshot_2015-12-17_14.14.53](/uploads/5d6ac28b6d99186485d727a72cc8a662/Screenshot_2015-12-17_14.14.53.png)

new
![Screenshot_2015-12-17_14.15.07](/uploads/06e07fa3716aa8664b1507b390270285/Screenshot_2015-12-17_14.15.07.png)

* Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/2577

See merge request !2151

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

Sidekiq-cron configuration moved to gitlab.yml

When `sidekiq-cron` was introduced, jobs configuration where placed
in `schedule.yml` file.

As discussed in #3928, this is not desirable. 
We moved it to `gitlab.yml`, exposing only the "cron" part of the configuration.

See merge request !2087

Fix MR 500 when viewing the MR page

Fixes #2712 

See merge request !2167

Explicitly require Nokogiri 1.6.7.1 due to security issue

```
Name: nokogiri
Version: 1.6.7
Advisory: CVE-2015-5312
Criticality: High
URL: https://groups.google.com/forum/#!topic/ruby-security-ann/aSbgDiwb24s
Title: Nokogiri gem contains several vulnerabilities in libxml2
Solution: upgrade to >= 1.6.7.1
```

See merge request !2154

Also, make it not fail.

This is required since we parse URI later and remove the credentials

Also adds a spec for MergeRequestHelper to avoid having a regression
later on.

[ci skip]

Fixed wrong URL to "up for grabs" issue filter

[ci skip]

See merge request !2162

Allow admin to create new user identities

Fixes #2442 

See merge request !2077

Fix issue related cross-project MRs

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/4188

See merge request !2163

Allow account unlock via email

We see a lot of users get confused about what it means when your account gets
locked. Many try to reset their password and are still faced with a lockout.
With this change, users receive an email that allows them to unlock their
account immediately. The previous behavior where the account is auto-unlocked
after a time also still works.

See merge request !2049

Show git version on admin page

Before
![git-version-beore](/uploads/57444ad42220c9dfe8f187b8e399227f/git-version-beore.png)

After
![git-version-after](/uploads/cc1b52ae1a251c2c46d9626c040726ab/git-version-after.png)

gitlab-org/gitlab-ce#4077




See merge request !2101

Fix build coverage regex matching to allow captures.

Fixes #2644 

/cc @DouweM 

See merge request !2138

Backport JIRA service

Fixes #3839 

Move EE JIRA functionality back to CE.

- [x] Make it function in manual testing
- [x] Migrate JIRA-specific tests
- [x] Tests pass
- [x] Migrate documentation
- [x] Rollback to previous CE JIRA integration locally, activate on a project then try to migrate db and see if integration still works.
- [x] Final EE search for JIRA references

See merge request !2146