The new gltf_viewer app has an optional zero-arguments mode whereby it
loads a resgen-embedded binary model, which is useful for quick
sanity testing. If you don't specify an IBL, it loads a compressed
version of the pillars IBL.
* Revert "Rollback MeshAssimp enhancements."
This reverts commit b3dce967eb.
* Re-enable glTF support
* Start looking for texture ids at 1, not 0
* Detect if the importer is glTF
* glTF and regular materials both work