Confidence bands for stochastic mass-action for Petri nets

[tim-at-topos]

For the stochastic mass-action analysis for Petri nets, it would be nice to have setting to run the simulation many times and visualise the variability across runs. For example, the plot could be changed to show, for each state, the mean as a line, plus the interquartile range as a confidence band.

Note. Currently, we automatically re-execute each analysis when the model changes. Liveness is a nice quality in a UI, but it will become more challenging to maintain as the cost of running an analysis increases (in this case, because the simulation is being run many times). We should be careful about this.

[quffaro]

@tim-at-topos I think I see three distinct features:

1. Running simulations whose parameters may be a range.
2. Visualizing some insight about different executions.
3. Naively, some component to conditionally stop simulation re-execution. WIP: Pausing re-execution of simulations #984

Do you agree?

[tim-at-topos]

I think this issue as I had meant it to mean is really focused on number 2, not so much number 1 (which is important but requires a lot of design thought)