Added basic workaround support for receiving private messages.

Implemented basic support for receiving private message, by simply
letting every channel fire a received message-event when a private
message from a channel user is received.
Of course you cannot receive messages from users that have no joined
channels in common with the local user. Also, the private message is
only recognizable by 'PRIVATE: ' and the ACTION-style formatting.
Clearly not desirable in the long run.
Added initial support for personal chat rooms.
Working on nick change support for personal channels.