Implement production cut in DepositionGeant4

Tentative for insert a production cut for secondary particles in DepositionGeant4. Resolves #94 (closed). As of now, I am setting the cut as one fifth of the smallest pitch/thickness among the detectors. In my opinion, this is a good compromise between performance and precision. The cut is inserted through the UI manager and it looks very dirty (but as far as I understand this is the only way to implement easily this cut). I would say that all of the implementation looks dirty.

This is just a try: let me know how you would "clean" it!