Simplify bikes_allowed handling

[flaktack]

Bike access handling in OTP2 could use a few simplifications:

• the internal models for Trip and Route have two fields for bike access due to differing GTFS fields (Trip, Route, BikeAccess)
• a default bikesAllowed values may be specified in GtfsBundle (which has a default of allowed), but its value may not be set from the JSON configuration (GtfsModule, GtfsBundle).

To simplify things:

• the mapping of GTFS trips.txt:bikes_allowed, trips.txt:trip_bikes_allowed, routes.txt:bikes_allowed and routes.txt:route_bikes_allowed can be handled when converting to the internal model
• Update Trip and Route to only have a single BikeAccess bikesAllowed field
• setting a default bikesAllowed value for Trips if none is provided could be removed