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.
Split up single script into a package with multiple modules.
Also add a setuptools control file. With this, stcgal can be
installed like any other program. It's still possible to launch
from the sources directly. stcgal.py has been converted into a
simple launcher.
v2: fix imports
