Add support for widgetApp: true

Add support for widgetApp: true

In the qmlproject file we support:
widgetApp: true

If this is true we use QApplication instead of QGuiApplication.
In some cases like usage of QtCharts QApplication is required.

This means if widgetApp: true is set we need to add a dependecy on Widgets and
use QApplication instead of QGuiApplication.

Because QApplication is heavier this is not the default.