WIP/DIRTY

First steps towards saving out the Jacobian on each time step.

Ideally, the various iterators (time integrator, nonlinear solvers)
should provide monitor functions that can be set by the user on each
time step.  However, this functionality is simple enough that it can be
exposed directly through parun.

The Parallel Jacobian list is managed by the Transport Model, not
the solver, so it is responsible for handling viewJacobian requests.

Also, PEP 8 fixes.