Show bus position on map, either simulated or using real-time data

[barbeau]

I opened this issue for OneBusAway Android (OneBusAway/onebusaway-android#176), and wanted to open a companion ticket here so we can track progress. Its not clear to me at this point whether we should implement something similar for OTP Android, or just direct the user to OBA Android. Having simulated position would probably make sense since this would be universal (as long as agency provides shapes.txt), but with real-time data we get more into the territory of OBA.

[kalon33]

It would be nice to extrapolate shapes.txt when it's not provided in gtfs, as it's the case in most gtfs files. Other people implementing a system to show bus on the map already do such thing.