[Cin] ChromakeyHSV menu much improved

[Andrea paz]

The patch works perfectly, as always with your work. The two plugins
are also perfect. More details I post them in MantisBT. I can't thank
you enough.

> Remember, any manipulations with alpha masks, including chromakeying, in
> CinGG require a bottom track with some opaque background, otherwise the
> transparent holes are displayed as if the same track without transparency be
> located under it. Although this behavior is sometimes confusing, I am not
> sure if it is a bug, and not done so by design.

Thank you also for your insight on transparency. I think it is an
important issue that recurs often in new user requests. I think the
other NLEs behave more intuitively however I am afraid that you cannot
make changes in CinGG without upsetting the program. Maybe add in the
manual the warning to use an opaque lower track when working with the
alpha channel. I noticed that if in the bottom track you disable the
“Don't send to Output” button, then the background color is correctly
black, but that is not a useful fact.