Support lifecycle events for non-builtin contexts

The original idea was to extend the API for context implementations to be able to notify the container of a context initialization / destruction. Based on this notification, the container would then notify the application by firing @Initialized(X) / @Destroyed(X) Object (where X is the scope annotation of the context - see CDI-86).

I don't think this double-notification approach is a good idea anymore. Instead, the specification should simply mention that the extensions providing an implementation of Context are encouraged to fire a @Initialized(X) event when the context is initialized and @Destroyed(X) event when the context is destroyed (again, see CDI-86 for details). Extensions are free to choose a payload that makes most sense for the given context (e.g. UIViewRoot instance for @ViewScoped) or Object otherwise.