GLTF loader

[trungtle]

Reposted @pjcozzi's comment to here:

For glTF support before GDC:

Reading and Tools

• To test a glTF model, drag and drop it here
• For an overview of glTF, see here
• For the full details, the spec is a short read (ignoring the properties reference)
• There are several JavaScript glTF, review the Cesium loader or others. Recall that the goal of our loader is to be as simple as possible and fully spec compliant so it can serve as a reference loader for everyone.

  Implementation

• Convert OBJs in this repo to glTF using OBJ2GLTF
• Remove the third-party WebGL loader (remove the file and reference in the LICENSE.md)
• Create a geometry-only glTF loader as a single.js file in the samples/third-party directory for now (we'll give it its own repo after GDC)
• Do not worry about loading shaders/texture/techniques/materials, animations/skins, cameras, etc. Instead, focus on walking the node hierarchy and loading the geometry.
• Research how well modern web browsers support data URIs. If support is still poor, use https://github.com/AnalyticalGraphicsInc/gltf-utilities