[Cin] ChromakeyHSV menu much improved

[Andrea paz]

I agree with your explanation; CinGG's way of treating the alpha
channel is fine.
Sorry, I was unclear because I (stupidly!) did not mention that the
white mask on a black background (the “matte”) is convenient only with
the “Show Mask” option of the plugin, and not during normal operation.
When setting up the mask, we need to see the lower track image to
adjust the edge and despill grading; however, although it is not very
important, seeing the matte in Show Mask is a small help in
highlighting the regularity of the mask we are going to create and in
discovering unwanted points of black in the figure to be extracted (or
points of white in the black background). However, if a user needs to
see the matte they can always turn on “Don't send to Output” on the
bottom track when using “show Mask.”

PS: in the manual, I wrote “Min Saturation” as the beginning of the
saturation range, while I wrote “Saturation Offset” as an additional
cutoff from the value of “Min Saturation.” I think I got it totally
wrong, also because of the bug that their effect looks the same.
Seeing your new plugin, the position of “Saturation Start” corresponds
to “Saturation Offset” and not to “Min Saturation” as I had written.
Seeing the code, can you confirm my mistake?

PPS: Is the new plugin (Avid) a total rewrite of Jerome's or just an
enhancement of the same code? I mean, do credits go to both Jerome and
Adam or just the latter?