GTFS Updates: Smart Updates & Storage

GTFS data is not updated automatically and will cause routing to fail if updated too early or not at all. We want to
1. automatically download and verify the correct GTFS data on setup/install/run
2. store non-current (old and future) GTFS data both locally and on S3
3. detect and switch out-of-date GTFS data files with new GTFS data automatically to ensure 0 downtime
4. ensure the server/graph-hopper replaces and rebuild all caches and graphs when new GTFS data is provided (bonus: without needing to restart the server or redeploy)