#454 Export Mesh As X3D: modify default settings

[Don Brutzman]

"Export Mesh As" X3D initially fails because the panel defaults are incompatible and incorrect.

Recommended changes:

• rename column title Vert to Vertices
• deselect both Normal outputs checkboxes as default because typical usage doesn't need them, or
• alternatively, just select Face Normals since that is 3x smaller
• make Vertices column and Face column mutually exclusive for X3D