Allow parkingSpaces only for wheelChairs

[palvarezlopez]

It's usefull for modelling "urban accessibility".

See #4411

[namdre]

this is somewhat difficult because parkingSpaces are for vehicles whereas persons in wheelChairs will probably be treated as persons.

[palvarezlopez]

And an attribute "VTypes_Allowed" or similar, to allow only a certain type of vehicle? (Transport of Wheelchairs, for example)

[namdre]

adding allow/disallow to a parkingArea could make sense (e.g. parking space reserved for trucks)
I'd probably use one of the custom vClasses for wheelChair-transports instead of adding a vtypes restriction to parkingAreas

Anyway, I'd let this ticket rest until the use case comes up.