GitLab

This commit includes changes to add `UserAccess#can_create_branch?`
which will check whether the user is allowed to create a branch even
if it matches a protected branch.

This is used in `Gitlab::Checks::BranchCheck` when the branch name
matches a protected branch.

A `push_to_create_protected_branch` ability in `ProjectPolicy` has been
added to allow Developers and above to create protected branches.

The API get projects/:id/traffic/fetches allows user with write
access to the repository to get the number of clones for the
last 30 days.

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

Markdown renderers find it easier to determine
where lists start and end when lists are surrounded
by new lines.

For consistency, also ensure entries in the list
are aligned when they span multipls lines.

Restructures existing page and adds improvements.

Document how runner applications are upgraded via one-click

Fixes gitlab-org/gitlab-ce#42595

For the sake of consistency, removes any extraneous
consecutive blank lines from the doc suite.

Add a line to say that event:read and project:read are required.
project:read is not strictly required right now, but will be when
the project dropdown is released next month.