CSG edit improvements.
Use cubic texture coordinate generation for the dual contour surfaces.
Merge branch 'master' of https://github.com/highfidelity/hifi into metavoxels
Merge branch 'master' of https://github.com/highfidelity/hifi into metavoxels
Merge branch 'master' of https://github.com/highfidelity/hifi into metavoxels
Merge branch 'master' of https://github.com/highfidelity/hifi into metavoxels
Merge pull request #3485 from ey6es/metavoxels

Improved CSG edit behavior for dual contour surfaces, use cubic texture coordinate generation.