Launch RAVEN search with Burst BBH events using CBC parameters; fixes #773 and #775

This MR adds the cWB BBH search as an additional search, treating it the same as the CBC search.

This entails:

• Adding a separate search looking for cWB BBH events when launching off a search='GRB' external event
• Launch GRB and subthreshold searches if lanuch off BBH event.
• Use the same time window as CBC events for BBH.
• Allow joint coincidences with BBH events during the O3 Replay.