[color-wallpaper] Interlink child and parent form layout
Summary: Should in some odd case (language) the color wallpaper's "Color:" label be longer than "Layout:" or "Wallpaper Type:" we can ensure the alignment between parent and child layout will not be broken.
This patch ie. alias works thanks to D20313.
Reviewers: Plasma, ngraham
Reviewed By: ngraham
Differential Revision: https://phabricator.kde.org/D20965