Clean-up stochastic process from unnecessary code lines inherited from original RAMP

[FLomb]

The file stochastic_process_mobility.py grounds on the original RAMP engine. As such, it carries forward some lines of code aimed at distinguishing the off- and on-peak probability of coincident switch-on of several appliances of the same kind owned by a single user. This is, however, completely unnecessary for RAMP-mobility, inasmuch as we do not account for the simultaneous use of multiple identical car by a single user. A household owning more than one car is just meant to be represented by several, individual users.

Therefore, we could clean-up that part of the code, removing it altogether and taking care of associated variables to avoid Errors.