Enable arbitration in MailRoom

Fixes #2870.

See merge request !1566

Tweak api doc

merge_request: add work_in_progress to MR hooks



See merge request !1443

According to `attributes_for_keys` and API doc, `POST /projects/:id/merge_requests`
is received `target_project_id` (NOT `target_project`)

Project names are not fully shown if group name is too big, even on group page view

https://dev.gitlab.org/gitlab/gitlabhq/issues/2548


![joxi_screenshot_1444408109183](https://gitlab.com/gitlab-org/gitlab-ce/uploads/c21ae245254b82db0212298b6f997067/joxi_screenshot_1444408109183.png)


See merge request !1561

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

Implement Commit Status API

This is preliminary implementation of Commit Status API, pretty much compatible with GitHub.

1. The Commit Statuses are stored in separate table: ci_commit_status.
2. The POST inserts a new row.
3. To POST execute GitLab API `post :id/repository/commits/:sha/status`. This accepts dual authorization:
- Using authorized user
- Using ci-token to allow easy posting from CI Services
4. This adds predefined variable to GitLab CI build environment: CI_BUILD_STATUS_URL, allowing to easy post status from within build (ex. with code coverage or other metrics).
5. This adds statuses to commit's builds view.
6. The commit's status is calculated taking into account status of all builds and all posted statuses.
7. The commit statuses doesn't trigger notifications.
8. The commit status API introduces two new privileges: `read_commit_statuses` and `create_commit_status`.
9. We still miss a few tests and documentation updates for API and CI.

@dzaporozhets @sytses What do you think?




See merge request !1530

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

cc @skyruler 

See merge request !1582

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

Ui improvements

* fix dashboard projects page for mobile
* fix project home page for mobile
* remove gray padding for small screens
* render no-ssh message same like we do for flash messages

cc @skyruler 

See merge request !1581

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

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

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

Refactor styles

cc @skyruler 

See merge request !1577

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

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

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

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

Refactor css structure

Related to #3025 

cc @skyruler @DouweM @rspeicher @vsizov 

See merge request !1571

Update changelog

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/1559
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/1558

See merge request !1576

Closes #2998

Signed-off-by: Kamil Trzcinski <ayufan@ayufan.eu>

Small typo fix when deleting groups