Support updating trip wheelchair accessiblity information via gtfs-rt
Keep track of update seen in the gtfs-rt feed
Don't run StoptimeUpdater in an infinite loop

the PeriodicGraphUpdate should take care of running it as needed
Add ADDED trips to the TransitIndex

Existing RouteVariants aren't used: a new variant is created for each
trip.

+ store TableTripPatterns in the index
+ add methods to add/remove GTFSPatternHpFactore.Result from the index
Return null on a non-200 http response
Store stopsSequences in TripTimes
Remove duplicate tripPattern per trip in transit index.
Let unit test GtfsRealtimeAbstractUpdateStreamerTest succeed again.
Add simple support for stoptime updates with delays
Add simple tests for StopTimeUpdater
Fix StoptimeUpdateTest
StoptimeUpdate: fix logging the number of applied updates
PeriodicGraphUpdater: catch updater exceptions
Stoptime Updates: Add TripTimes.State to store the source/status
gtfs-rt: avoid null value if feed failed to fetch
TransitIndex - basic computation of Stop#direction