Predefinition of data paths and time slots as requirements

Predefine data paths and time slots of VLs as constraints for the solver. This should enable the reuse of older generated NAP configurations. For example when an old configuration has still unused time in between slots new VLs can use this space without changing the previous slots.

- Define new input for scheduler and change input schema file for scheduler/verifier
- Use predefined slots as constraints for scheduler
- Add verifier checks that the predefined slots are still in the same position
- Should the predefined slots already define the full path of the VL or should it be allowed to predefine only some slots?