[Bf-funboard] Texture/Image nodes

[Robin Allen]

I thought perhaps the Texture node-tree could share some nodes with the 
compositing tree; there are nodes like Mix, RGB Curves, Blur, Rotate, 
Flip etc. which it would seem wasteful to re-implement for textures.

I did some poking around in the code and it seems the nodes are tied 
pretty heavily to whichever tree-type they're designed for. Now, I'm not 
greatly familiar with the code yet, but it seems to me we should either:

* Make some of the more generic compositing nodes into 'common' nodes 
which can be used by any tree type. Come to think of it, this would be 
almost all of them.

-or-

* Rename the 'compositing' tree-type to a generic 'imaging' tree-type 
and use this type for both Textures and Compositing. That way all (or 
the most appropriate) new compositing nodes will be available for use in 
texture generation, and vice-versa. I only suggest this because almost 
all of the compositing nodes are just general image-editing functions.

Maybe someone with more node codebase (nodebase?) experience than me can 
suggest which would be the best way to go?