gltf model rendering:

AssetFile::DrawModel (program):

* loop over all scene nodes
  * call DrawNode()
		* assembles matrix for the node
			- either via mat44
			- or assemble mat44 from SRT
		* if have mesh
			call DrawMesh()
			* loop over all primitives
				* gather primitive attributes
					- get dimension
					- get attribute type (position, normal, texcoord)	
					- get stride
					- set attribute pointer
					- enable attribute
				* get accessor
				* bind buffer using accessor
				* get primitive mode
				* draw array using primitive mode and accessor
				* disable attributes
			
		* if children
			recurse DrawNode()
	
