Room perma-bans and improved duration selection

Permanent bans are now available as an option when banning a user from a room. Additionally instead of a text field, I've added a set of pre-defined duration options.

Starting at 1 hour, going up to 3, 12 and 24 hours, 7 days up to permanent. Permanent bans are, in fact, 6 months which is equivalent to site-wide perma-bans.

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