Review: Added two additional Nuke OCIO nodes

Jeremy Selan <jeremy...@...>

* LogConvert, which is a handy node that does the colorspace transform
between the SCENE_LINEAR role, and the COMPOSITING_LOG role. While
this isnt strictly needed (it could be accomplished using the
ColorSpace node) it's convenient for the artists to have so they dont
have to worry about all the options. They can just think, "give me
the right log to lin".

* FileTransform, which allows for the application of individual files
(i.e., luts). While not needed in general use, this will let users
apply any lut that OCIO knows about, independent of the normal OCIO


-- Jeremy