This patch reworks all the packet processing to use the new
Packets objects. Nuked all of the messaging classes.
backwards incompatible changes
all messaging.py classes are now gone and replaced by
packets.py classes
This patch updates the main aprsd threads class to use
a shared queue to notify all aprsd thread classes they need
to exit. This ensures any closing down of sockets, etc happens from
inside the context of the thread itself, not the MainThread that
calls stop.
This patch creates a threads directory and separates out
the contents of threads.py into separate files in the
threads directory to make it easier to find and maintain.