Add reversevomap.py script to generate default list of allowed_vos (SOFTWARE-2670)
Add reversevomap.py script to generate default list of allowed_vos (SOFTWARE-2670)

For testing purposes, this is a separate script; the code will be moved
into utilities.py once I'm done with it.

matyasselmeci/osg-configure,opensciencegrid/osg-configure,matyasselmeci/osg-configure,opensciencegrid/osg-configure