customize persontrip.transfer options within a personTrip

[namdre]

different trips might use different settings (i.e. normal taxis vs bike-sharing)

Maybe with a new personTrip attribute that lists all the active options: <personTrip transferCarWalk="parkingAreas"/>

Problem: Right now the global transfer options are applied directly to the routing graph. We either need to keep multiple graphs around (possibly a lot) or instead define a graph with maximum connectivity that filters dynamically depending on personTrip attributes.

related to #5929, #11186, #10921

[namdre]

The solution "graph with maximum connectivity" is already supported via AccessEdge filterings on trip->modeSet and trip-vClass