Gfind refactor

@cmillion - I've refactored gFind to allow it to be called from either the command line or via an import in a user's script.  Other minor updates include swithing to argparse instead of optparse, adding a "quiet" option, and a few additonal parameter sanity checks.

I've regression tested this a bit, both on the command line and as an import.  Could you please further regression test this version of gFind and, if everything looks good, merge this branch with master? (the only file changed on this branch should be gFind.py anyways)

Thanks.