Added option to add Java properties to the Jython interpreter invocation...

....

This is especially useful if you want to set the Jython cache file to a folder
that your process controlls.  E.g.:

  $ gsh.jython -p "python.cachedir=$CACHEDIR" myscript.py

The shell wrapper will create a command line like:

  /opt/jython/bin/jython -Dpython.cachedir=/path/to/cachedir myscript.py