Added permission control plugin

Plugin allows assigning users to ranks and can list all the ranks they
have assigned. Comes with 3 extra permission nodes:

rank.[name].add - Allows giving that rank
rank.[name].del - Allows taking that rank
getrank - Allows listing ranks of a user

Also modified the permission manager, permission nodes and rank names
are now case insensitive and a wildcard at the end of a given permission
(such as rank.guest.* to give both add and del) is supported. Also added
a co-owner rank which can take admin status from users.