PyInterpreter: always add location of the startup.py - script to sys.path
PyInterpreter: always add location of the startup.py - script to sys.path

This patch will try to locate startup.py using Path::find() and add
the corresponding path to the search path for python. In this way, we
should always be able to load the startup script even if the installation
is in a strange place.

tkemmer/ball,tkemmer/ball,tkemmer/ball,tkemmer/ball,tkemmer/ball,tkemmer/ball