Revamp the userlist to support multiple rooms

Again, they are created on-demand before any other triggers should execute
Another autoban overhaul

Reason and !ab'er are logged and can be checked by mods

New !ab syntax: !ab <user>, <reason>, where the reason is mandatory
New command: !cb (in PMs, it's <user>, <room> and in a room it's just <user>)
  to check the current ban status of <user>

Banlist checking syntax is still banlist <room> and only in PMs, but I might
merge this into the !cb command.