Re-Simulation Processor #49

We already have two generators that require an input file formatted the same as our event files and these generators attempt to restore the configuration of the random number generator in Geant4 at the time of the first simulation.

I've been trying to use these generators to do some re-sim and it isn't working.

I think this is because the Simulator processor is designed to be the first Producer in a production chain. I think we can get around this issue by writing another processor that is specifically focused on re-simulation. This processor would be designed to provide the current event bus to other simulation parts before starting the simulation, so that Geant4 can be reconfigured the same. Then we can run the ReSimulator processor as the first Producer in an analysis chain.

This will probably require some modifications to other parts of our simulation infrastructure. Another potential solution is to try to have the Simulator work for both running modes; however, I ran into issues trying a few "easy" fixes, so I think separating them will be easier.