Separate X and Y passes of blurring like it's done for flat
gaussian blur. This reduces computing difficulty from size^2
to 2*size without any visual changes in matte.
Merge keying node from tomato branch into trunk.
It was considered stable and helpful by Mango team and it'll help
studio pipeline, because nodes would stop disappearing when opening
files in current trunk.
Full information about keying nodes could be found there:
http://wiki.blender.org/index.php/User:Nazg-gul/Keying
