Print summary of grouping/sorting run.

def prt_summary(self, prt=sys.stdout):
        """Print summary of grouping/sorting run."""
        # Grouping summary
        fmtstr = "Grouped: {U:3,} User GOs, using {h:2,} of {H:,} Grouping GOs, for run: {NAME}\n"
        prt.write(fmtstr.format(
            NAME=self.grpname,
            U=len(self.usrgos),
            h=len(self.hdrobj.hdrgos.intersection(self.hdrgo2usrgos.keys())),
            H=self.hdrobj.num_hdrgos()))