Fix tone reproduction curve estimation

The ITUR_2100_PQ_FULL.ICC has no colorants and revealed the bugs.
Iteration order was inverted so normalization didn't work.
Also only the first colorant was ever written, and
consequently the luma coefficients were also incomplete.

Additionally, RGB vs. BGR channel ordering was not respected,
and the sum of luma coefficients needs to be 1.0 for HSY
color space calculations.

And while at it, calculate a few more points so the graph in
the color space browser looks at least somewhat like a curve.