Draft: Add support for PBR maps (specular, normal, metalness, roughness, emittance)

[leMaik]

I've been working on this for a while (since christmas 2020), it actually took so long that I added support for metalness and roughness in the meantime. The normal mapping only recently became feasible after switching to normalized quad block models.

For testing, launch with:

• -Dchunky.pbr.specular=labpbr (default) or -Dchunky.pbr.specular=oldpbr
• -Dchunky.pbr.normal=labpbr or -Dchunky.pbr.normal=oldpbr

The maps are multiplied to the Material settings, so you'll have to set specular, emittance and metalness to 1 for all blocks and smoothness to 0 (ie. roughness to 1). You can launch Chunky with -Dchunky.pbr.updateMaterialDefaults=true to do that.

Mixing PBR formats is not yet supported (we need some way to specify that per resourcepack).

[jackjt8]

Working as intended. Looks really cool