Added full TOX room support.

This implements MUCRoom.
Note you need : https://github.com/aitjcize/PyTox/pull/34 for now as PyTox implementation is late.

Some things are weird because TOX supports anonymous Rooms and you
cannot join a room with beeing invited.

Another gotcha: this is weird to invite somebody because you need to
know what is the roaster number of the contact.