###  chat off
###  chat <channel # or name>
   changes your channel on the dcc chat connection.  when you first
   connect to the bot, it places you on channel 0 (the party line).
   you can move to another channel where basically nobody can see
   you (except anyone else who decides to join that channel).  valid
   channel numbers are 1 thru 99999.  some channels may have assigned
   names -- for those, you can specify the channel by name instead of
   number if you wish.

   'chat off' removes you from any channel at all.  you can still
   use normal bot commands and see the console, but you can't talk
   to anyone except via '.note'

   'chat on' returns you to the party line (channel 0) if you were
   elsewhere.
