This adds the button to create a new mirror on the dashboard at the same
place where "new repository" and "new organization" already exist.

This is follow-up for 56c66ee486 allowing admin
to see private repositories, even when not being member of them.

The hyperlink and the display name of the branch if the branch is in a folder or the branch name has '#'

This allows the admin to disable the version information about gogs and
go in use in the footer.