Instantiate the SCDL model catalogue in the context of schema-app.coffee (prior to instantiating window manager) and made changes to allow either a class or a function to be specified for the hosted observable window in a window manager layout. If a class is specified window manager creates a new object instance and hosts it. If a function is specified, window manager calls the function and hosts the object instance returned. The later case is useful for things like the SCDL catalogue that are not tied to a specific window manager window and are viewed in many different ways.