Expose QApplication::layoutDirection property from QML

This property can be used to query the default layout direction of the application. On system start-up, the default layout direction depends on the application's language. The property has value Qt.RightToLeft in Arabic and Hebrew locales, where people scan and read graphic elements and text from right to left. In Western cultures the layoutDirection property is Qt.LeftToRight by default. Contrary to QApplication::layoutDirection, in QML this property is readonly.