Use nativeResourceForIntegration "rootWindow" to get the appRootWindow

As the native interface can provide the root window it's better to use
that instead of going through QDesktopWidget.

Change-Id: I0a7b475b5ef2a802f603b29762bf2d9033dfa13d
Reviewed-by: David Faure <david.faure@kdab.com>
remove QtWidgets dependency

The module doesn't depend on QtWidgets any more.

Change-Id: Ic8036ec1ee53ef8b1a3bb6c827fb815f322865a2
Reviewed-by: Martin Gräßlin <mgraesslin@kde.org>
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Fix hard dep on widgets for autotests

Change-Id: I4a847eb9480eb6343fe60c71ec3e37bd6887af9f
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Merge remote-tracking branch 'origin/stable' into dev

Change-Id: I6d27c3ef1242de08a8b9b6ee619c942982d3384c