fix(auth): let the ban of a section take the permissions of that section
A ban of a section took nothing away through the permissions, so whatever a section guards by a permission alone stayed open under it: a member banned from the comments still uploaded pictures for news comments, and a moderator banned from the guestbook, the library or the comments went on moderating them. BanVoter now takes away the permissions of the section a ban is for, above what a guest may do, as it does with all of them under the full ban.