[quickshare] Port configuration window to QQC2 and Kirigami.FormLayout
Summary: This patch ports quickshare's configuration window to QQC2 and Kirigami.FormLayout, as well as matches the General category's icon with the applet's icon.
Reviewed By: VDG, apol, ngraham
Subscribers: abetts, apol, plasma-devel
Maniphest Tasks: T10586
Differential Revision: https://phabricator.kde.org/D19664