Summary: This patch aligns the color wallpaper plugin's options with the FormLayout above it by making use of twinFormLayouts.

Test Plan:
D19932 needed before testing.

Before:
{F6719634}

After:
{F6719629}

Before:
{F6719633}

After:
{F6719630}

Reviewers: #plasma, ngraham

Reviewed By: ngraham

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D20048