This made sense in ppsim with its multiple methods of simulating, but it seems like a distraction now that we only have the one simulator class. It somehow seems cleaner to have a single simulator class and perhaps specify different options to it, for example once we get Gillespie step working, we could tell it always use Gillespie, but that doesn't require a whole new class, just a Boolean field.
This made sense in ppsim with its multiple methods of simulating, but it seems like a distraction now that we only have the one simulator class. It somehow seems cleaner to have a single simulator class and perhaps specify different options to it, for example once we get Gillespie step working, we could tell it always use Gillespie, but that doesn't require a whole new class, just a Boolean field.