QML on Android doesn't support multiple windows, so dialogs that work on
the desktop are not a good solution on Android. A much more natural way to
present sub windows is a stackView.
In order to do this Preferences needs to be an item and the structure of
the ApplicationWindow needs to change a bit.
This also removes the hard coded sizes and instead tries to design this in
a resolution independent manner.
The diff appears larger than the actual change because of an increase of
indentation for the ApplicationWindow content.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
