add channels to peers and swarms

- closes #27 
- moves ppspp_channel:get_channel/1 to ppspp_channel:where_is/1 using gproc
- uses a more prudent 60 sec timeout for selecting a new random channel rather than ~ 30 minutes, although its not clear where this code would actually run yet
- add lookups for swarm id and swarm options to swarm_worker
-move message_SUITE to handshake_SUITE as that's actually what it has become