FCPClientReferenceImplementation.subscribe(): Consume new interfaces

Adaption of DebugFCPClient to pass instances of thew new interfaces will
follow.
FCPClientReferenceImplementation: Document GC policy of passed objects
DebugFCPClient: Add skeleton of new event handlers

Notice: start() cannot use the Java  7 diamond operator, otherwise the
compiler would complain:
" no instance(s) of type variable(s) T exist so that argument type
DebugFCPClient.BeginSubscriptionSynchronizationHandlerImpl<EventSource>
conforms to formal parameter type
BeginSubscriptionSynchronizationHandler<T>"