Blender Git Loki

Simple hair children: Make twist affected by texture

This completes twist feature, which is now possible to also control by
texture. Since textures can not easily contain negative values as well,
same trick with 0.5 neutral as vertex groups is used.

All in all, this twist features allows to do following things.

Original hair:

{F2287535}

Hair with scientifically calculated twist value of 0.5:

{F2287540}

And we can also twist braids in opposite directions dependent on left/right
side:

{F2287548}