Removal of RGB Rendering Model

[callan]

The RGB rendering model is a holdover from the client side rendering engine that doesn't fit well with the colour choices one would like to make. Having to flip the rendering model when one wants to assign channel 0 to blue, channel 1 to green and channel 2 to blue explicitly is less than ideal.

The real benefit this has is allowing an optimization to be enabled when you don't have colour component overlap in the user's colour choices. The rendering engine should be smart enough to enable this optimization based on the user's colour choices and not have to have the rendering model flipped by the API user.

In short, the model should be removed and the optimization enabled intelligently by the rendering engine.

[callan]

Largely resolved as part of r1574, the actual removal of the extra code will come in milestone:3.0-Beta3.

[callan]

Just hasn't been a necessity to remove this in milestone:3.0-Beta3, moving to milestone:3.0-Beta4.