prop: Configurable number of coeffs for each plane.

Set to the default it has always been, {25, 1, 1}.
Further testing of other defaults to follow.

It is a pretty bad API right now since it assumes 27-dimensions.
wht: Apparently forgot to add the .c file.
Fix some warnings in common files.
prop: Use YCrCb and a 10-3-3 coefficient scheme.

Seems to offer the best time-accuracy tradeoff.

0.04% worse accuracy but improves running time (mostly build-time)
by ~21% compared to 16-4-4 YCrCb as used in the original paper.