Configurable random seed

[n-peugnet]

Like #72, the random seed Peersim parameter is for now hard codded and there is no wait to change it. I think this parameter has no reason to be a Ppi one but there is still a problem with it. By default Peersim uses the given seed for the first execution and then pick a random one for the next execution. We changed this comportment by overriding the random seed in the following executions. We can keep this modification but it would be good to make it an option.

Now the question is: Where do we put this option.

I think we could have in Ppi config file this structure:

{
    "deploys": [],
    "undeploys": [],
    "calls": [],
    "options": {
        "peersim": {
            "configFile": "peersim.properties",
            "reuseRandomSeed": true
        }
    }
}