A Singleton IView implementation.
In PureMVC, the View class assumes these responsibilities:
IMediator instances.IMediators.INotification in the application.IObservers to an INotification's observer list.INotification.IObservers of a given INotification when it broadcast.Constructor.
This IView implementation is a Singleton,
so you should not call the constructor
directly, but instead call the static Singleton
Factory method View.getInstance()