Implemented ManagerInterface in AccountManager and CharacterManager

ManagerInterface was already designed for those two anyway. The only thing
left to do is to rewrite the room API, and the whole thing should work
fine again.

I still think map data should be saved and loaded by lua code, so the
rooms will still implement lua hooks. There may be other things that can
be loaded from SQL, but I don't know what.
finished rewriting the room API