Updated custom shader framework

[gajop]

This probably does it: jk3064/Custom-Unit-Shader-Framework#1 (also see Flove)

[gajop]

Due to some critical optimization improvements also merge stuff from BAR and use newest (dev) engine.

[gajop]

Not sure if I'll have the time to get stuff from BAR. Hopefully will but might require fiddling to get someone else's code integrated cleanly!