* Combine RGBA
Basically the opposite of separate RGBA, brings 4 value channels into a single
RGBA image). Has interesting possibilities for reordering channels, when used
with separate RGBA!
* Dilate/Erode
Originally written by Brecht van Lommel, with some minor modifications and
tweaking by myself. Positive distances dilate, negative distances erode.
* I also added the 'value' field to the hue/saturation node. Minimal extra cost,
and can be handy.