Freight: Add a CarrierJob interface

[kt86]

and put CarrierService and CarreirShipment behind it.

This is a first steps on the way to

1. store the Jobs, nomatter wheter it is a Service or a Cshipment (helpfull for logistics)
2. It is a first step, to reduce code, by putting more and more commen things in here and
3. allign CarrierServices and CarrierShipments a bit more
   See also issue: Freight: Introduce something like a "CarrierJob" on MATSim-level #3510

@JWJoubert, @rewertvsp: I added you as reviewers, so you can a) get an info about this change and b) can comment on the name of the interface. 'CarrierJob' was just my first idea.