Show merge requests which close current issue

Closes #2903

### What does this MR do
If an issue is to be closed by a merge request the current user has access to, this will be displayed when the user looks at the issue.

![Screenshot_from_2015-10-12_12-10-37](https://gitlab.com/zj/gitlab-ce/uploads/52e429704e73067b24b69801f13ad7bc/Screenshot_from_2015-10-12_12-10-37.png)

/cc @DouweM

See merge request !1569

Close issues mentioned in MR description when MR is merged using
fast-forward merge or when merge commit message is edited.

Fixes gitlab-org/gitlab-ee#48.

See merge request !1639

Fix bug where a push would only create cross references from the first commit.

Apparently we can't `return` from a `Hash.new` block. Who knew.

See merge request !1638

See merge request !1623

Hide Builds tab is GitLab CI is not enabled
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !1627

Redirect old CI project route to GitLab project
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !1629

Fix padding of outdated discussion item.

Old:

![Screen_Shot_2015-10-16_at_09.29.17](https://gitlab.com/gitlab-org/gitlab-ce/uploads/d715debebe54d27c2eed7c22843e886c/Screen_Shot_2015-10-16_at_09.29.17.png)

New:

![Screen_Shot_2015-10-16_at_09.29.23](https://gitlab.com/gitlab-org/gitlab-ce/uploads/7c0c033adade92cb16406c027cb4c010/Screen_Shot_2015-10-16_at_09.29.23.png)

It still looks the same when the discussion is expanded.

See merge request !1614

Temporary bring /ci page page with help information
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !1630

Separate rendering of Markdown reference links from redacting those the user doesn't have access to and extracting referenced objects

Related: !1014

See merge request !1090

Allow dashboard and group issues/MRs to be filtered by label

See merge request !1591

Use gitlab-git-http-server 0.3.0 for GitLab 8.1

See merge request !1605

Track compatible gitlab-git-http-server version

The 'git archive' changes in GitLab 8.1 require a version of
gitlab-git-http-server that is incompatible with GitLab 8.0, so we
need to keep track of this now.

See merge request !1603

Improve typography



See merge request !1622

Dont put padding on typography but on holder elements instead

Fixes wrong padding of wiki content.

See merge request !1620

Make selectbox options more compact
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !1619

Highlight comment based on anchor in URL
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Fix for #2954 

See merge request !1618

Add index on ci_commits.gl_project_id



See merge request !1616

Add a system note and update relevant merge requests when a branch is deleted or re-added

If a branch is deleted with an open merge request, amended offline, and then pushed again,
GitLab doesn't bother to update the merge request even though the last commit ID and/or
code may have changed. This MR ensures that each push will update any relevant merge
requests and adds a system note if this happens as well.

The new messages look like:

![image](https://gitlab.com/gitlab-org/gitlab-ce/uploads/6581eea069cd8e485b7fa4187ed4c043/image.png)

Closes #2926 

See merge request !1601

Implement when syntax in .gitlab-ci.yml

See merge request !1606

[ci skip]

Also adds a preamble note that a working 8.0 installation (i.e.,
gitlab-git-http-server, updated Nginx/Apache configs) is required before
proceeding.

[ci skip]

[ci skip]

Sentences end in periods.

[ci skip]

See merge request !1604

Prepare 8.1 documentation

[ci skip]

See merge request !1612

Update redcarpet gem. Fixes gem memory leak

Fixes #2773 

See merge request !1607

Build View UI fixes



See merge request !1608

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

Markdown typography CSS fixes

The `!important` flags recently added to the `md-typography`
mixin's `pre` elements were overriding the background and
foreground colors for syntax highlighting.

| Before | After |
|:------:|:-----:|
| ![Screen_Shot_2015-09-25_at_3.32.32_PM](https://gitlab.com/gitlab-org/gitlab-ce/uploads/802163bd9f46864ac89e7be165951f07/Screen_Shot_2015-09-25_at_3.32.32_PM.png) | ![Screen_Shot_2015-09-25_at_3.33.30_PM](https://gitlab.com/gitlab-org/gitlab-ce/uploads/6be72036653378405320085324dff5ad/Screen_Shot_2015-09-25_at_3.33.30_PM.png) |

See merge request !1442