Few fixes to the sensor type code.

In ComputeAlignment.py:
- removed unnecessary line future_builtins.SensorType= "Timepix" before checking
options.sensor
- fixed bug in print statement (wasn't printing!) regarding 180 degree rotation

In Constant.py:
- made the comment more specific to avoid confusion with Timepix = Timepix1 and
Timepix = all kinds of Timepix chips