pyInterface: some deWeight.py bugfixes

changed outputFileName to a mandatory command line argument, kept the weights
in the deweighted files (were deleted before) and did some minor
changes/improvements.
pyInterface: some convertTreeToEvt.py bugfixes

make outputFileName a mandatory argument. Expand environment variables for the
particleDataTable path (make default pdt path work). Enclose opening the output
file with a with statement. Some more minor bugfixes/improvements.
pyInterface: some convertEvtToTree.py bugfixes

make outputFileName a mandatory command line argument. Change naming
conventions to current coding style. Print all command line arguments at some
point. Some more minor bugfixes/improvements.
not ready