Terminate method

[artgoldberg]

Create a terminate() method for SimulationEngine.simulate(). A simulation can terminate in multiple ways, such as run out of events, exceed end time, trigger stop condition, or raise an exception. In some cases, it would be useful for a simulation run to perform certain actions before terminating. Example actions include:

1. Before terminating take a checkpoint that could be used for debugging
2. Open an interactive session that could be used to inspect the simulator

I imagine that terminate() could

• execute some events scheduled for the end of the simulation
• perform some tasks that are not simulation events
• and exit

[artgoldberg]

mv to de_sim