GitLab

The following formerly separate commits have been merged in:

* Adjust 'Sign in' button for GitLab's CSRF protection

  GitLab introduced CSRF protection for authentication requests in
  571ba5a7. The 'Sign in' button has been
  adjusted to send a POST request.

* Opt out of turbolinks for 'Sign in' button

Resolve "Create a tab shortcut to jump directly to content"

## What does this MR do?
Adds accessibility shortcut to page, i.e. if user hits `tab` key right after the page is loaded and user has not interacted to any part of the page, the shortcut appears at top left corner of the page. Then, pressing `enter` (`spacebar` support is WIP) scrolls page to focus on content.

## Are there points in the code the reviewer needs to double check?
See if `id` attribute added to `.content` element (present in [_page.html.haml](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/views/layouts/_page.html.haml)) needs to be reviewed if it is correct approach or we already have an ID that shortcut can refer to.

## Why was this MR needed?
This feature is particularly useful for screen readers where user doesn't have to go through entire nav to reach content of page.

## Screenshots (if relevant)
![Screenshot_from_2016-11-17_17-59-22](/uploads/0eb0149f46bd35e9ce629e7a6533be53/Screenshot_from_2016-11-17_17-59-22.png)

## Does this MR meet the acceptance criteria?

- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?


Closes #24057

See merge request !7533

see #22343 for issue description

Closes #12797

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

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

Closes #18543

This reverts commit 13e37a3e.

Closes #18542

Added a button into the sidebar for issues & merge requests to allow users to manually create todo items

Closes #15045

This reverts commit 3e991230.

# Conflicts:
#	app/models/project.rb

When there are 0 Todos, the Todos icon still had the blue badge with a "0" in it, which made me think I had a new Todo left. This makes it less annoying.

Follow-up on !4077.

Closes #14477

Closes #14259

Prevent Groups to have smaller visibility than projects
Add default_group_visibility_level to configuration
Code improvements

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

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

Code was failing because branch was named `'test'` with quotes
which was escaping the javascript I was using.

Also adds autocomplete="off" to find input.