With the introduction of real abstract classes, it is not possible
anymore to instantiate StcBaseProtocol. Instead, extract some of the
code for autodetection into the new class StcAutoProtocol and use
that for autodetection.
This adds various tests, integrated into setuptools. These use "monkey
patching" where needed to mock the pyserial and packet reader/writer
functionality to allow for testing with no changes.
The code should be refactored to simplify testing, but this is good enough
to stop regressions for now.
