Sample PyVista plots for Clawpack/GeoClaw

Created by scripts in clawpack/visclaw/dev_pyvista directory on pyvista branch.

This is work under development, and still needs to be cleaned up and generalized for inclusion in VisClaw; see the comments in Issue 311.

Sample topography showing effect of subsidence or sea level rise

Created with geoclaw/Quillayute/Quillayute_sealevel.py showing the mouth of the Quillayute River at La Push, WA (Quileute Tribal Nation).

See also new html versions that allow the viewer to manipulate on the web.