Residual norm plotting

[cwentland0]

Right now, the only means of tracking the iterative solve and steady solve residual norm is via the output to STDOUT. This is not very useful, especially when the numbers are streaming past at a fast rate. It would be much preferable to plot the time history of the residual in semi-log to get a better visual, especially for convergence of the steady solve. This will have to be a separate class from ProbePlot, but it may be useful to create a shared parent class which governs time history plots.