Vcs dv3d separate plot constituents updated

Adds dual input scalar plots and enables separate configuration of plot constituents (e.g. surface, volume, slice).

Must also merge Vistrails branch:     uvcdat-dv3d-Fix_parameter_issues
ok good to know.
On that note we now have the the repo: https://github.com/UV-CDAT/uvcdat-testdata

If it's not gigantic it might be worth storing these sort of things there. Also in a separate branch/issue you might want to move all the pngs there.