#4511: Add Gratia probe for GridFTP

We need to add the Gratia probe for GridFTP.

It's available from
<https://twiki.grid.iu.edu/bin/view/Accounting/ProbeInstallation>. As I
write this, the version is 1.00.5c-2. We don't need to update the other
probes for now.

This should be installed when we install Bestman. For now, we won't
install it with GridFTP by default, just with Bestman.

It requires Python >= 2.3.

Big note: It reports to a different collector.
gratia.opensciencegrid.org:8886

The batch collectors report to:
gratia.opensciencegrid.org:8880

The difference is so we don't overload the collector for job
information. I don't know if this affects configure_gratia or not. We
don't hard-code host names, but we do have port numbers in there. It may
require documentation changes and coordination with the GOC. We need to
figure this out.

This probe was released as a new package in 1.10.1q.