Cost file

If user wants to directly simulate a functional of stationary distribution, this one must provide a file containing the different cost values for each states. Numerotation can indifferently begin from 0 or from $1$, but output simulation results correspond always to a numerotation beginning from 0.

For example, this 'cost' file corresponds to a model with $10$ states (numeroted from 0) and $3$ cost classes.