https://github.com/imageworks/OpenColorIO/pull/73

Replacing some pre ocio code for building luts at drd

- Added new OCIO::Baker interface and initial pass at houdini lut writing
- Added new app ociobakelut which is a light wrapper around OCIO::Baker
- Exposed the FormatRegistry to the rest of the core so that OCIO::Baker can access format->Write()
- Added GetFileFormat() which will return a format based on nickname
- Modify the truelight test data so that it looks more like what comes out of truelight

.malcolm