* Curves that are of type BOOL or STRING will now never be able to change the keyframes interpolation to something else than CONSTANT.
* Removed the classes Custom_Knob and Custom_KnobGui which were redundant with String_Knob.
* Natron now supports OpenFX Custom params interpolation.
* Added a default OpenColorIO config which corresponds to the nuke-default. By default all  plug-ins using OCIO will have the color-spaces LUT available from the nuke-default.
Merge branch 'workshop' of github.com:MrKepzie/Powiter_Core into workshop