OBJLoader n-gon support

Gltf2 material extras

AssimpLoader: Refactoring

remove unused variables

3DS Loader texture support

[gltf] Refactor loadMeshes.

Includes changes necessary to support the upcoming Draco extension, and more glTF primitive types.

Add the 'rebeccapurple' color

This little change updates the list of color names to be compliant to the CSS Color Level 4 spec, specifically by adding the only missing color: 'rebeccapurple'.

Some history behind the color : http://www.metafilter.com/140112/A-hue-angle-of-270-degrees-a-saturation-of-50-and-a-lightness-of-40)

Fix hardcoded reference to material[ 0 ] with currentMaterialSlot

Fixes to Maya exporter

- Export materials before meshes, so they can be applied to faces.
- Raise an error on faces with > 4 vertices instead of writing JSON
  which will fail to load.
- Correctly export transparency -- black in Maya means opaque.

Updated layers doc to remove reference to masks

Examples: Clean up

Fixed display dashed lines in SVG renderer #11879

make DOF work again.