OIIO

[antond-weta]

This is a proposed replacement of the 'rawtoaces_util' library and 'rawtoaces' command line tool.

Main changes:

• Uses OpenImageIO instead of LibRaw for reading raw files.
• Uses OpenImageIO instead of AcesContainer for writing OpenEXR files.
• Uses OpenImageIO instead of the bespoke code for command line parsing.
• Uses std::filesystem instead of boost::filesystem.

The makefile contains 2 new targets rawtoaces_util2 and rawtoaces2. The old targets are still in place.