ISM/OM timestepping order: which comes first?

[RupertGladstone]

Currently the ISM run method is called first then the OM run method, with a sequential model. If we stick with sequential it might be best to run the OM first since FISOC may calculate the geometry change rate to be passed to the OM based on the geometry from the ISM in the last 2 timesteps. This means that, with the current ordering, the change rate will alsways be zero the first time the OM is called. We could reverse the OM/ISM ordering or we could make the order a user choice at runtime.