Don't drop stop_times with invalid location_type

[traines-source]

I feel that completely dropping stops from stop_times that have a location_type other than 0 is a bit harsh.

gtfsparser/mapping.go

Line 1209 in 38dc406

panic(errors.New("Stop " + a.Stop().Id + " (" + a.Stop().Name + ") has location_type != 0, cannot be used in stop_times.txt!"))

While it may be invalid according to the spec, it should not do any great harm to routing or sth. On the contrary, dropping stops from trips does have quite a negative effect. E.g. currently in the DELFI feed for many ICEs heading to Hamburg, which, since Hamburg is dropped, appear to only go till Hanover: https://api.transitous.org/?tripId=20250329_11%3A23_de-DELFI_2766990098 (DELFI feed from 20250224, trip_id 2766990098, stop_id de:02000:10950:5:2549012). There are many more such invalid stops in the current DELFI feed, see mfdz/GTFS-Issues#72.

So I think this should be made optional or just a warning.

@jbruechert