Redesign config pages

Summary:
Redesign the KDE Connect and Bluetooth pages as well as some adjustments to all pages

Before:

After:

Bluetooth is basically identical

Reviewers: VDG, apol, ngraham

Reviewed By: VDG, apol, ngraham

Subscribers: abetts, ltoscano, kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D19646