Condense UI of the Specific color selector
This diff moves selection of color space into a popup, as suggested in
bug 362952. It also changes the 'Use percentage' checkbox to a toggle
button, to further condense the controls.
The layout is now in a designer form.
Adds new SVG icons for 'ratio'.
Reviewers: Krita, rempt
Reviewed By: Krita, rempt
Subscribers: rempt, scottpetrovic
Differential Revision: https://phabricator.kde.org/D16724