[FifteenPuzzle] Port configuration window to QQC2 and Kirigami.FormLayout and improve UI
Summary:
- Port to QQC2 and Kirigami+FormLayout
- Use radio buttons to choose color vs image
- Disable inactive controls appropriately
Test Plan:
Everything still works.
Reviewers: VDG, Plasma, GB_2, filipf
Reviewed By: VDG, GB_2, filipf
Subscribers: GB_2, filipf, plasma-devel
Tags: Plasma
Maniphest Tasks: T10586
Differential Revision: https://phabricator.kde.org/D20747