Port from KPassivePopup to KNotification

Summary: KPassivePopup is hideous and shouldn't be used any more. Replace it with a persistent KNotification

Test Plan: Click on tray icon: Notification appears. Start a tea: Notification changes content. Click tray again, notification disappears

Reviewers: sboehmann, dakon, broulik, fb, dfaure, davidedmundson

Reviewed By: davidedmundson

Subscribers: kde-utils-devel

Differential Revision: https://phabricator.kde.org/D22542