plaster/lime-plaster Unreal ORM pack

Files:
- baseColor.png: import with sRGB enabled.
- normal.png: set compression to Normalmap.
- orm.png: R=Ambient Occlusion, G=Roughness, B=Metalness, sRGB disabled.
- height.png: optional parallax/displacement source.

Dielectric materials use a black Metalness channel.
