Adjustments > Color: new Tint tool

Needed to match the availability of Tint as a quick-fix option.

As with all quick-fix tools, this dedicated Tint tool provides a better
final result, as it attempts to preserve overall image luminance despite
the changes in green channel light.  Also, it allows for a wider range
of changes than the quick-fix slider.

As part of this commit, I have also moved the Temperature tool from the
"Lighting" sub-menu to the "Color" sub-menu.  That seems a more natural
arrangement, given the new temperature/tint duality.