AveragedTurbine, ScalarODE physics

I'm yet to be certain that I don't have a flaw in AveragedTurbine residuals, and I need to add some missing terms to the Jacobians, but the intrusive changes look to be in good shape now.

This probably shouldn't be merged until the scalar_residuals branch goes into libMesh, but it should actually compile against older libMesh just fine; it just won't give correct results.
Hmm. Perhaps I over-engineered the naming? Or should we add a `misc_init` method or something?