changed decayTopology to fix genPseudoData.py

Since the implementation of the eventFileWriter into genPseudoData.py the
arguments of decayTopology's methods (which took ROOT Objects) were
impractical. Change the Python wrapper as well as the source files to
reflect the new handling. The changes in genPseudoData are minor.
pyInterface: genpw.py -> eventFileWriter

Implemented eventFileWriter into genpw.py. Still unsure if Comgeant output parts
should remain (only commented out for now).