GTFS Realtime

[mattwigway]

GTFS Realtime feeds for BART and MBTA are already in the database. However, using them in graphs/deployments is a bit tricky, because of opentripplanner/OpenTripPlanner#825, and also because it is tricky to know what feed to map the real time data to. Following conversation with @novalis, it appears this will be difficult; GTFS-rt is matched to GTFS by agency_id, which may be the defaultAgencyId we set or may be an explicitly-overridden agency ID. To complicate things, just grabbing agency_ids out of GTFS won't help, because, for instance, BART has two agencies in their GTFS (BART and AirBART, although the Oakland Airport Connector may change that) but does not report agency_id in GTFS-rt. Trip IDs are feed-unique, but once a graph is built we don't know what feed a particular agency came from.