Avoid splitting when not necessary as it may incur in performance hit. Indeed,
splitting means more (tinier) goals to verify, hence more call to provers.

- Add support for neural network as array in language.ml
- Translate csv record as vnnlib constraints in dataset.ml
- Add simple dataset normalization functionalities in dataset.ml
- Add vnnlib printer (as smtlib printer with direct real support)
- Add vnnlib driver for PyRAT
- Rework onnx and nnet parsers to not fail on non-mandatory information