Fix manufactured solution viz step

[xylar]

This merge fixes the manufactured solution viz step following #236 to account for new directory names and to include the time step as well as the resolution in plot panels.

A few other small pieces of clean up are also included for convenience.

Checklist

• Testing comment in the PR documents testing used to verify the changes

Fixes #248

[xylar]

Testing

I was able to run the manufactured solution convergence_both test with MPAS-Ocean on Chrysalis. (The analysis step fails as usual because the tolerance is not met.) The result of the viz step is:

Note that the time step as well as the resolution are plotted on the left.

[cbegeman]

Thanks, @xylar! This looks great. Approving by visual inspection

[xylar]

Thanks @cbegeman!