(excuse the typos in the actual commit msg)

Added TestForDDImageVersion.cxx to FindNuke.cmake so that we can workout which version of nuke we are building against. This now gets appended to the '$CMAKE_INSTALL_PREFIX/lib/nuke${Nuke_DDImageVersion}'. This makes it easier to build and run against multiple versions of nuke.

Added init.py and menu.py so that the ocio nuke plugins can be setup with the NUKE_PATH searchpath, to make it easier to test and integrate into our toolchains.

Updated the INSTALL file to reflect these changes.

https://github.com/malcolmhumphreys/OpenColorIO/commit/8d45b1dd71b845cc3b685263f365f25358ad8c68

.malcolm