Improve curvature map generation

[and-rad]

The way curvature maps are currently created leaves a lot to be desired. Most popular and widely known ways to do curvature in Blender produce significantly worse maps than Substance Painter does.

• https://www.youtube.com/watch?v=-FNxXrm0uzo
• https://www.youtube.com/watch?v=syqKuPTanGM
• https://blenderartists.org/t/the-pointiness-value-dissected/674328/4
• https://blender.stackexchange.com/questions/94187/adding-edge-wear-to-relatively-low-poly-mesh
• https://docs.blender.org/manual/en/latest/render/shader_nodes/input/ao.html