Start integrating a second-pass shader for custom block models
Update for textured block-models
Initialize custom geometry when textures are available - working UV texturing on plane faces
Test a translucent non-solid block model

Ref https://github.com/deathcap/voxel-mesher/issues/5
Ref https://github.com/deathcap/voxel-shader/issues/2
Expose setTestGeom() for easily testing model changes live when debugging
Move the custom test geometry to the middle of the voxel, like a glass pane
Custom geometry test: full 3D, 1/16 block high, resting on ground

Requires deathcap/block-models@b066a16bdf2b70fa45e18f1917cebd9e9e85db5c
Render custom models from voxel-mesher. Ref GH-4

Requires deathcap/voxel-mesher@9c9cc67995bad2f06f1e4c6de8e0ebed10afc539
Ref https://github.com/deathcap/voxel-mesher/issues/5
and https://github.com/deathcap/voxel-ideas/issues/3