Since the introduction of the sidebar, DefaultFileDialog.qml has used
Qt.labs.settings to store user-adjustable state.  It's important to
note that applications should control the location of these settings
by setting the name, organization and domain.

Change-Id: Ia5dd5ce5d172c345738b48b41e945d834cc143a5
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>