Add a few predefined variables to CI builds

This adds CI_BUILD_TAG, CI_BUILD_STAGE, CI_BUILD_NAME and CI_BUILD_TRIGGERED to build environment.

This change is based on: !1530 

See merge request !1572

Fix: Images cannot show when projects' path was changed

Fixes #1443

See merge request !1521

Revert "Improve invalidation of stored service password if the endpoint URL is changed"

This reverts commit b4639754.

See merge request !1595

This reverts commit b4639754.

Improve invalidation of stored service password if the endpoint URL is changed

A number of issues were found in !1490 and !1558 (triggered by support request 7395)

* It is not possible to set a new URL and a password at the same time (new password is ignored)
* An error occurs on the Service Templates admin pages (prop_updated? was referencing the service's project, which is not defined for templates)
* Passwords are reset on every save in Service Templates admin pages

This should fix these 3 issues by respectively:
* Differentiating a property that has been assigned a new value (regardless of the new value) and a property that has been assigned a new value that is different from the old one
* Providing an alternate implementation to detected updated properties, not relying on the service's project
* Filtering an empty password parameter passed to the Service Templates admin page like on the project service page

See merge request !1583

Fix retry and cancel for build

This fixes some regressions introduced by Commit Status API

See merge request !1586

It now allows to specify a password at the same time as the new URL, and works
on the service template admin pages.

+ and Titleize New Project button on dashboard

Hello there. Its my first merge request in open source world. So please be tolerant to me if i do something wrong.

I try to fix https://gitlab.com/gitlab-org/gitlab-ce/issues/2906

See merge request !1564

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>