Blender Git Loki

patch from Bjørnar Hansen (anachron)
Multiple background images displaying each on a different axis.

Changes made from the original patch.
- Use an enum rather then multiple booleans.
- Reduced the space taken up by the user interface.
- Made the image template compact display not show fields & premul options.
- Added readfile.c lines so old blendfile images are loaded.
- Option to hide BGpic UI (like modifiers & constraints)
- Use the index rather then a bgpic from the context for the remove operator.

note: could be good to use 1 image for both left+right, for eg, but for this to work as intended we would need to add image flipping depending on the axis so left this commented out for now.