Automatically set "MonteCarlo" as stochastic.type when a background simulation is launched

A minor request, which could reduce the list of checklist before to start a Monte Carlo simulation.

A typical work situation in Migri is to launch a background Monte Carlo simulation in the evening and let it run overnight. The model has to be saved with the "stochastic.type" parameter = MonteCarlo.

The problem is that before launching a Monte Carlo simulation, usually the user simulate the model has "Mean" to test the changes in properties. It can happen that the user forget to switch the stochastic.type from Mean to MonteCarlo.

Usually a model takes several minutes to be simulated, and that means that it is not possible to understand quickly if the stochastic type is wrong, until you go back to your simulation results in the morning and there are no results.

For this reason I would suggest to allow Migri to set as default stochastic type the "MonteCarlo" type when a background simulation is launched. Even if sometimes you may want to use another stochastic type for background simulation, I think this is the most common.

I think this would reduce the amount of things to check before running a routine simulation.