Proof of concept of a wayland protocol to allow the keystate dataengine to work

Test Plan: Tested with both the lock screen and the keyboard indicator plasmoid

Reviewers: #kwin, davidedmundson

Reviewed By: #kwin, davidedmundson

Subscribers: davidedmundson, kde-frameworks-devel

Tags: #frameworks

Differential Revision: https://phabricator.kde.org/D20191