Make a CondorVersionInfo from a set of version integers. #3856

Add a new constructor for CondorVersionInfo that takes the broken-down
components of a Condor version: integers for the components of the
version and an optional char* for the build date and other trailing
info.
This is useful for the gridmanager and ft-gahp to feed default peer
versions into the FileTransfer object for backwards-compatibility.
Add CONDOR_VERSION command to ft-gahp. #3856

The file transfer protocol changed in 8.1.0. Newer daemons/tools need to
know when they're talking to an older peer or else transfers will fail.
Since the gridmanager and ft-gahp reside in different machines, it's
very possible that they will be different versions.
Thus, the ft-gahp and gridmanager must exchange version strings and feed
those strings into the FileTransfer object.
Add CONDOR_VERSION command to gridmanager. #3856

The file transfer protocol changed in 8.1.0. Newer daemons/tools need to
know when they're talking to an older peer or else transfers will fail.
Since the gridmanager and ft-gahp reside in different machines, it's
very possible that they will be different versions.
Thus, the ft-gahp and gridmanager must exchange version strings and feed
those strings into the FileTransfer object.
The gridmanager will always issue the CONDOR_VERSION command to a GAHP
that supports it.