Several things are accomplished in this commit, including:
- Use OIIO instead of our own functions for pixel format conversions
(cleaner code/less for us to maintain)
- Fold all PixelService functions into the PixelFormat class
(cleaner code)
- Moved OpenGL pixel definitions to OpenGL classes and out of the
global classes.
- Add support for RGB buffers as well as RGBA (optimization)
Implementation isn't perfect yet, viewer/renderer doesn't update yet when
the preference is changed so a sequence needs to be re-opened for the change to
take effect.
itsmattkc