Provide generation and individual id to objective in snes

[jakobj]

This PR change the call of the objective function in snes to provide generation and invidividual id to the objective functions. This information is required, for example, to set random seeds within the objective function. @mschmidt87 please have a look at this.

[jakobj]

regarding your comment in #5: to reduce complexity (using inspect), i would like to avoid a check like this. the only drawback for the user if they do not need individual and/or generation would be that they need to capture those values in the function call: def objective(z, *args) instead of def objective(z). i think the advantages of having these values available if requires outweigh the disadvantages here

[mschmidt87]

I agree with you, after all, your solution seems simpler, therefore approved.