Other texture types

TODO: Cubemaps exist, are pretty much universal, and some effects might even want to use them. What would it take to hook everything up? Would these just be another paint to supply to the established fill patterns? On that note, although less widely available, some other things like volume textures, texture arrays, et al. would have similar questions.

These almost certainly need to be spelled out in the kernel declaration, since the appropriate samplers need to be added to the shader headers. Presumably bad effect assignments can be intercepted with the information this makes available as well.

This is low-priority.