User roles control

Folks with 'owner' role should be able to set/remove 'moderator' or 'administrator' bits on other users.

Frontend
Simplest thing for now is to have a user-role control button on the profile page, alongside the block/moderate/etc controls.

Need to be able to:
 * set/unset moderator
 * set/unset administrator

Perhaps show as a popup menu like the moderator controls, with state buttons for each inside?

For now we don't need a big user list or anything.

Mockup
Maybe something along these lines?



Backend
This part's easy!

$user->grantRole($role); $user->revokeRole($role);