Added new railcar for powdered goods (like cement)

You can now couple cars freely. (1.7 funcitonality)
You have to download locs separately.
Removed capability to transport passengers, run the service in technical manoeuvres.

Added a passenger capacity to all cars. If you don't want these cargo trains to behave like passenger trains you have to set the line to 'run empty trains', else it'd break passenger behaviour either way.