Copies over David's implementation in Klipper and integrates it in the
plugin. To do so it splits the ClipboardListener class into 2
subclasses: one that uses QClipboard and the other that uses the
DataControl classes.
BUG: 359747
Summary: Added a timestamp to track clipboard changes, so when a new device connects it will sync the most recently updated clipboard to both devices.
Reviewers: #kde_connect, albertvaka
Reviewed By: #kde_connect, albertvaka
Subscribers: albertvaka, sredman, kdeconnect
Tags: #kde_connect
Differential Revision: https://phabricator.kde.org/D22584
