O4a online dtdphi plotter

This patch allows the following dtdphi plot to be uploaded to gracedb page.
Example G-event pages:
MDC 3-ifo event (two dtdphi plots)
MDC 2-ifo event (one dtdphi plot)
MDC 1-ifo event (no dtdphi plot)

TODO:

• test with single triggers
• test with online small analysis
• try adding LV plot and see if that is informative any way

gstlal-inspiral/bin/gstlal_ll_inspiral_event_plotter

@@ -529,7 +529,7 @@ class EventPlotter(events.EventProcessor):
 			fig = plotdtdphi.plots_dtdphi(ifo1, ifo2, snrs, horizons, sngl={"dt":dt_ref, "dphi":dphi_ref})
 			filename = '{}_dtdphi_{}.{}'.format(event['gid'], ifo_pair, self.format)
 			if not self.no_upload:
-				lvalert_helper.upload_fig(fig, self.client, event['gid'], filename = filename, log_message = 'dtdphi 2D pdf plot', tagname = 'dtdphi')
+				lvalert_helper.upload_fig(fig, self.client, event['gid'], filename = filename, log_message = 'dtdphi 2D pdf plot', tagname = ('dtdphi', 'background'))
 			if self.output_path is not None:
 				filename = os.path.join(self.output_path, filename)
 				logging.info('writing {} ...'.format(filename))