unauthenticated packets were subject to having their hashes stripped
just like other packets. The problem is that they don't have hashes to
strip, so I was throwing away part of the packet. Fixed in log.py,
dmrlink.py and bridge.py
As of now, dmrlink.py is only a behind the scenes worker... It's just
the base class to take care of link establishment and maintenance.
Applications, such as bridging or logging will now be in their own
files and inherit from dmrlink.py
