Doc : improve the presentation of multi simulation

[benoitgaudou]

Describe the improvement you'd like The way to manipulate experiments, in particular how to display information on the same graph needs to be improved, in particular in the page : https://gama-platform.org/wiki/RunSeveralSimulations

Add a mention to permanent in this page.

[lesquoyb]

Hello, I updated the page for multi-simulations: here Can you check if that's ok to you ?

[lesquoyb]

I also updated the batch documentation page about permanent, not sure it's the best example but still better than before I think

[lesquoyb]

Closing it, feel free to reopen if there's something missing/wrong