Adding stochastic simulation group and stochastic simulation methods

The history is weird. I started by adding the getSeed() method, and then made some errors in trying to merge with the latest version of RoadRunner which I fixed. Each of the simulation methods got written up and submitted as a single commit, but I had accidentally added backup files and documentation in previous commits which I removed.

As a result, the history looks really ugly. If it's too ugly, I can turn all the commits into one single commit and re-submit a pull request.