[Cin] Chromakey improvements checked in to GIT

[Phyllis Smith]

Thanks again to Andrea.  I had to make a single change as my Latex got an
error on:  ($#ff000000$).  I had to remove the 2 $ to solve it.

> To add the explanation of the new keys and equalize the presentation
> to what was done for ChromaKey-HSV, I updated the manual for the
> ChromaKey plugin. You just need to replace the entry in Latex.
>
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