'glTF' Format Support

[Mirsario]

Tracking issue for the state of glTF support. Pretty bare-bones so far.

• Meshes with various primitive types
• Nodes / Transformations
• Skinning Data
• Animations
• Cameras
• Images & Textures
• Lights (KHR_lights_punctual extension)
• Materials
  • KHR_materials_pbrSpecularGlosiness extension