* Added 'active node' panel for the Nodes Editor. This panel, in the NKEY region, shows the settings for the active node. Included in this panel is a field used for editing the unique-name of the node too.
* Fixed a number of uninitialised vars warnings that I missed in previous commit...
* Compo node backdrop works again.
* Compo node previews and backdrop now get correct color management
float to byte conversion.
* Compo nodes got unecessarily recalculated while moving nodes.
* Fix compo node viewer nodes not getting activated correctly.
* Main compo node preview render computations are now outside of
mutex lock, so better for multithreading.
* Tex node outputs did not work in some files loaded from 2.4.
* Change RNA updates to take into account groups that may be shared
between multiple node trees.
Added RGB space distance matte Node
Added HSV color matte Node
Fixed Image difference matte Node to use image differences instead of RGB space distance
Fixed luminance node for low end values being read wrong
Fixed CMP_util copy/swap functions not accounting for all channels
Fixed UI for difference matte Node
Added RNA for new nodes
