Plot Overlap Integral and Odds Ratio for External Coincidences

Similar to how we are currently plotting the bayes factor and coherence from bayestar, we should plot the overlap integral (in general) and odds ratio (for only CBC-GRB search, not subthreshold GRBs).

These info would just be to assist the RRT with making decisions about events rather than to trigger anything automatically.

These both can be computed used tools in ligo.raven.search and info already available in superevents w/ coincidences.