Improve the Qt5 QtQuick template and make it available in CMake as well

Summary:
* Uses resources instead of relying on executing the application in the source
directory.
* Uses QQmlApplicationEngine instead of QQuickView
* Doesn't introduce weird logic as if the user had to learn QML by looking at
the template.

Reviewers: kfunk, #kdevelop

Reviewed By: kfunk, #kdevelop

Subscribers: kfunk, kdevelop-devel

Differential Revision: https://phabricator.kde.org/D4721