Added the ability to flush the 3D render cache to allow changes that are only known from outside the renderer.
Added the ability to flush the 3D render cache to allow changes that are only known from outside the renderer.

MatterHackers/agg-sharp,mmoening/agg-sharp,larsbrubaker/agg-sharp,LayoutFarm/PixelFarm,mmoening/agg-sharp,jlewin/agg-sharp,mmoening/agg-sharp