Show the resolution of the app, not the size of the screen it is running

on (or not)

Change-Id: I8fd28cfa567b5bcd49373f7400dfc366adf80b6d

qml/widgets/Resolution.qml

@@ -1,5 +1,5 @@
 import QtQuick 2.6
 
 Widget {
-    text: screenSize.width + "x" + screenSize.height
+    text: appWindow.width + "x" + appWindow.height
 }

src/main.cpp

@@ -88,7 +88,6 @@ int main(int argc, char *argv[])
     qmlRegisterType<PictureModel>("PictureModel", 1, 0, "PictureModel");
 
     engine.addImportPath("qrc:/");
-    engine.rootContext()->setContextProperty("screenSize", app.screens().at(0)->availableSize());
     engine.rootContext()->setContextProperty("fileReader", new FileReader(&app));
     engine.rootContext()->setContextProperty("nativeHelper", new HelperFunctions(&app));
     engine.load(QUrl(QStringLiteral("qrc:/main.qml")));