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