Blender Git Loki

* Added buttons for accessing options "occlude", "backface cull" and "bleed", note that bleed is 0.0 by default, before it was always 2.0;
* use a faster method of getting a pixels screenspace location.
* check if its possible to break out of pixel to bucket/face intersection early - ~7% overall speedup (ignoring redraw time).
* removed scanline intersection function (added back incase they were needed but it looks like there not)
* speedup for painting with only 1 image (use a loop without context switching checks)
* more commenting + cleanup