Start/stop : Quality fixes and geojson export

Start/stop config feature:

• for a start/stop configuration, there is now a geojson file created that contains all the stops for that route and trip_id, with changing trips there can be more or less stops as stops can be skipped/added based on the (time of) day. This can be used in a map card along the verhicle position.
  Note: documentation update still t.b.d

Start/stop config quality improvements:

• for realtime vehicle tracking, the geojson file contained an id with the trip_id to make it unique, this led to a lot of orphaned entities when they were removed by the geojson integration after the trip ended. Now it uses the vehicle_id to make it unique (if vehicle_id does not exist, it will still take the trip_id as basis) and this allows geojson entities to be reused much more often and thus substantially reduce orphaned entities. Since the name of the entity changes (slightly) this may lead to a reconfig of the card(s) that you are using
• RT calls failed with an error when there was no next trip, now this is properly avoided.
• For realtime data at a stop, it used the expected arrival time at the stop as RT time-stamp but in case of longer terminal stops or a layover, that would be incorrect as the RT departure could be many minutes later. Now the RT time-stamp is chosen as the latest between RT departure and RT arrival times.

All of this thanks to @Pulpyyyy