Hide Uploads button unless user has adequate permissions

If the user doesn't have the mf-uploadbutton permission, which is
typically restricted to autoconfirmed users, don't show them the
uploads button in the left menubar.

Also fixing a comment in the process.

Bug: 62598
Change-Id: I56e10f032330fabee74fcfbb5ab3939e118e3968
Merge "Hide Uploads button unless user has adequate permissions"