Scale quantizer values to full range when enabled

[rzumer]

We support passing color range via the color config settings, but there is no change in how the video is processed at the moment. Quantizers should be scaled by the factor by which the range of values increases when going from limited to full range. As raised by @tterribe.

[rzumer]

Tested scaling the DC and AC quantizer values by 255/(235-16) (full range/limited range), which provides about -0.5% BD rate improvement on nyan.y4m (scaled to full range with ffmpeg).

However, this scaling also improves BD rate of the limited range clip, so I am not sure how to interpret these results.