Add a new endpoint in the new API for creating a new pipeline, and return the details of that pipeline.

[ci skip]

Allow `order_by` and `sort` parameters to `/api/v3/groups.json`. At
present, only ordering by name and path is supported, and the default
sort is name ascending (alphabetical order).

The JSON of the example responses were missing a few `,` and therefor
invalid. This adds them to make those JSONs valid.

It adds a button to the branches page that the user can use to delete
all the branches that are already merged. This can be used to clean up
all the branches that were forgotten to delete while merging MRs.

Fixes #21076.

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6342#note_17981448

[e44da1c] Add Label API expected keys to tests

[ac929c8] Update Label API documentation

Signed-off-by: NRémy Coutable <remy@rymai.me>

[ci skip]

[ci skip]

The UI allows to define a token to validate payload on the target URL,
this patch adds the feature to the API.

Signed-off-by: NRémy Coutable <remy@rymai.me>

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/440

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

The /licenses, /gitignores and /gitlab_ci_ymls endpoints are now also
available under a new /templates namespace. Old endpoints will be
deprecated when GitLab 9.0.0 is released.

Signed-off-by: NRémy Coutable <remy@rymai.me>

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

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

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

Signed-off-by: NRémy Coutable <remy@rymai.me>