Module environment sanitization

Since the plot and reset calls from Proa may load all kinds of modules and even
modify the module search path, I now sanitize both of these. This should
allof for a more uniform call environment. Furthermore, the pythonPath from
the config file is injected into the path before the parameter files of
each job are parsed.

Testing of datafiles for modification and conditional postprocessing
has been cleaned up. I really need to document this...