Absolutize the path of nnet given to provers

See merge request laiser/caisar!11

           - more robust
           - fix a perhaps why3 change

CAISAR on top of Why3

See merge request laiser/caisar!6

[Marabou] Fix driver for valid and invalid result in order to consider the negation of the conclusion (as for every SMT solver).

          Disjunction handling in verification is not needed

Onnx parser

See merge request laiser/caisar!8

   - All the case are run (i.e don't stop at first true disjunction)