Update RGG and Nuclide defaults and dependencies

Minor build changes:

1. Make RGG session off by default
2. Make RGG session dependent on ParaView
3. Make Nuclide application dependent on RGG session

Warnings:

• please consider adding a changelog entry in a file ending with .md in doc/release/notes.

The warnings do not need to be fixed, but it is recommended to do so.

Do: test

This merge request has been queued for testing. Test results may be viewed on:

• CDash (release)
• Buildbot (release) (only visible from inside Kitware)

Branch-at-release: 96c7e985

@tjcorona Are we still good with this?

assigned to @tjcorona

+1

Do: merge

mentioned in commit 11ae96f8

merged