Objects on the lookup implementing ModelRefreshListener (not an API) will now be notified.
Updated the specification of NbListenerRef because it was too strict in many practical cases.
Added a utility API class: NbListenerRefs.
Project nodes refresh requests during extension activating/deactivating are collapsed into a single node refresh. Also, the project node is always refreshed if a new extension gets active or inactive.
Extensions using the old API will now benefit from project model cache as well (assuming the content of their lookup is serializable).