[x3d-public] [popbuffer-test] crytek-sponza

[tom sparks]

i've been testing pop-buffer with meshes from 
http://graphics.cs.williams.edu/data/meshes.xml

* Used blender to convert the obj/mtl files to x3d

Issues:
* source meshes have no geometry instancing, manual geometry instancing 
too slow :(
* no priority loading in X3DOM
* loading hidden submeshes (need a better LODer)

Bugs?:
* pop-buffer boundary box seams too big for submeshes


test: <https://tomasparks.github.io/X3D/popbuffers/crytek-sponza/index.html>