This patch implements a new stats collector paradigm
which uses the typing Protocol. Any object that wants to
supply stats to the collector has to implement the
aprsd.stats.collector.StatsProducer protocol, which at the
current time is implementing a stats() method on the object.
Then register the stats singleton producer with the collector by
calling collector.Collector().register_producer()
This only works if the stats producer object is a singleton.
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.
Hemna