Makes methods virtual and adds override, ref #176.
Adds selected  necessary member variables from abstractnavigation, ref #176.
Completes updateCamera(), ref #176.
Implements resize event for materialcanvas, ref #176.
Implements MaterialWidgetEventHandler::sceneChanged coorectly for loading scenes into the materialcanvas, ref #176.
Adds getter and setter for bounding box radius in MaterialWidgetEventHandler, ref #176.
Adds more necessary member variables to MaterialWidgetEventHandler copied from ArcballNavigation, ref  #176.
Copies 2 needed functions from ArcballNavigation to MaterialWidgetEventHandler, ref #176.
Adds to MaterialWidgetEventHandler::mousePressEvent() left mouse press recognition and ignores other mouse press interaction, ref #176.
Disables Arcball interaction if releasing the left mouse button in materialcanvas, ref #176.
Enables the left mouse arcball interaction while moving the mouse with left mouse key pressed, ref #176.
Replaces the ArcballNavigation with working MaterialWidgetEventHandler in materialcanvas, closes #176.