NTFS - Modification of the school_vehicle_type field about navitia

[antoine-de]

I also think transport_type is better than school_vehicle_type.
@stifoon ?

[pbougue]

@stifoon @prhod where are we on that? any hope to handle that subject? any need?
Should we close it?

This implies doc modif, and changing code to allow both at first, maybe later remove support for school_vehicle_type, and soome coordination with @eturck who's probably producing/using some NTFS too. Light work.

[eturck]

We are not using school_vehicle_type. You can do whatever you want 😃.