Port to Qt 5.14 + Android

Summary: There's a series of things that should be done differently nowadays on Android.

Test Plan: Tested the application on my Android phone.

Reviewers: #android, vkrause

Reviewed By: #android, vkrause

Subscribers: vatra, vkrause, kde-edu

Tags: #kde_edu

Differential Revision: https://phabricator.kde.org/D27715