parkingArea rerouters improvements

[lcodeca]

One of the bottlenecks of the scenario generation is the rerouter computation between the parking areas.

The script in question is: https://github.com/eclipse/sumo/blob/master/tools/generateParkingAreaRerouters.py

[lcodeca]

Try to use the --bulk-routing option in duarouter to compute all the possible routes between parking areas.