Hah this took a while, as there was no texture scaffolding in place at
all. Thus all this had to be added and tested for the first time:
* 2D textures
* 2D texture arrays
* Texture transformation uniforms
* Texture transformation UBOs
* Instanced texture offset
This also means that MeshVisualizer can be used to visualize arbitrary
(single-channel) integer textures now, not just render meshes with
object ID textures. Yay for feature parity!
Vladimír Vondruš