Add Vehicle as a property generator

[AWbosman]

Vehicle is a tool specifically designed for generating properties beyond local robustness.
We want VERONA to be able to work with Vehicle.

First step is to add VEHICLE as a local robustness vnnlib generator as this should create a single independent file.
In later steps we have to deal with the tree of either/or clauses. This probably will only work after we get the GPU connectivity such that we can actually cancel ongoing queries.