Blender Git Loki

Compositor upgrade;

- Links now can be made between any socket type. The nodes recognize amount
of channels, and will convert types if needed.
Conversions from RGBA to 1 channel will use the 'RGB to BW' formula.

Also note that conversions only happen when required. So you can blur an
alpha channel, filter it, and put this in a 1-channel socket without any
conversion to happen, which saves memory & cpu time.

http://www.blender.org/bf/rt.jpg

The blur nodes don't accept Vector input yet... But filter does.

- RGB Curve Nodes now have the premultiply option resored, 2 x faster

- Fixed some confusing code in Node Group handling... much stabler now