remove PacketMultiplexListener, RoomListenerMultiplexor and
ConnectionDetachedPacketCollector(Test), which was a bunch of
(in same cases redundant) code that formed a complex construct that
presumably tried to make MultiUserChat instances easily garbage
collect-able.
Now, MultiUserChat should be eligible for gc if the userHashLeft() is
invoked before the reference to the instance is dropped, which should be
the case in the most scenarios. Otherwise the connection may references
the MultiUserChat instance over Packet(Listener|Interceptor)s preventing
the gc.
365c71db79