Edit group members via API

Fixes #1840.  Implement a new API endpoint to update the access level of an existing group member.  Includes new tests and updated API docs.

cc @sytse @douwe

See merge request !1504

Add an API endpoint to update the access level of an existing group
member.

Revise main README for cleanup and some minor clarifications

Update Emoji Cheat Sheet Link

The emoji cheat sheet link was changed. Commit changes the url to the
updated link and fixes issue #8554.

Fix link to SSH help page.

Closes #1981.

See merge request !1502

Fix Issue 1064

Fixes broken doc links within the installation section, as described in:

https://gitlab.com/gitlab-org/gitlab-ce/issues/1064

See merge request !334

Don't allow page to be scaled on mobile and add horizontal scrolling to code blocks

Closes #1974.

Previously, scaling (both automatically and manually) was enabled on mobile, which caused the top and sidebar to move over content. Scaling is now disabled.

Also previously, code in issues or comments too wide to fit inside the width of the window would "flow out" on the right, causing the whole page to become very wide and causing scrolling to scroll the entire page instead of just the code. Code blocks now scroll themselves.

See merge request !1501

Actually submit comment on command-enter.

Resolves #1869.

Because !1474 didn't actually work.

cc @sytse

See merge request !1499

Closes #1981.

Resolves #1869.

Bump gitlab shell

See merge request !1497

Add label notes

It creates system note, when someone changed labels of issue/MR.

Just look at the screenshot:

![labels](https://gitlab.com/uploads/vernik91/gitlab-ce/ebbdba6bdc/labels.png)

Solves this [request] (http://feedback.gitlab.com/forums/176466-general/suggestions/6623258-create-a-note-when-issue-labels-change).

*P.S. Thanks this [PR](https://github.com/gitlabhq/gitlabhq/pull/8237) for idea 😉. But I need this feature as soon as possible.*

See merge request !331

Extend issue clossing pattern

New: "Resolve", "Resolves", "Resolved", "Resolving" and "Close"

Now matches those supported by [GitHub](https://help.github.com/articles/closing-issues-via-commit-messages/), with the addition of the -ing forms.

See merge request !1475

Cleanup gitlab example

Fixes #1938

See merge request !1495

Add internal broadcast message API.

See gitlab/gitlab-ee#241.

Used by gitlab/gitlab-shell!53.

See merge request !1486

Add index on order columns for services table

See merge request !1492

Bug fix for default issue tracker

See merge request !1493

Changelog description

Please merge before tomorrow.

See merge request !1491

Improve release guides

* move update docs to separate file to prevent mess with rc tasks
* update patch release guide
* update GitLab.com when packages are done. No need to wait 2 days

See merge request !1490

Improve OAuth UX

See merge request !1489

Added a note saying inline HTML is disabled by default