Add OCIO

OpenColorIO integration: load and handle Lut files and Colorspace changes.
Colorspaces available from nuke configuration: linear, sRGB, sRGBf, Cineon, Gamma1.8, Gamma2.2, Panalog, REDLog, ViperLog, AlexaV3logC, PLogLin, SLog and raw.

Before launching Duke, export the OCIO configuration file with:
export OCIO = "~/duke/dependencies/nuke-default/config.ocio"

Use the --outputspace and --viewinglut commands to use OCIO.
example for Colorspace changes:  ./src/duke/duke ~/Desktop/video.*.exr --outputspace Cineon
example for Luts files: ./src/duke/duke ~/Desktop/video.*.exr --viewinglut ~/pathtoluthile/luts/cineon.spi1d
The default Colorspace is linear.