code: public <T> T actorFor(final Class<T> protocol, final Class<? extends Actor> type, final Object...parameters) {
      if (isTerminated()) {
        throw new IllegalStateException("vlingo/actors: Stopped.");
      }
  
      return stage().actorFor(protocol, type, parameters);
    }
docs: Answers the {@code T} protocol of the newly created {@code Actor} that implements the {@code protocol}.
  @param protocol the {@code Class<T>} protocol
  @param type the {@code Class<? extends Actor>} of the {@code Actor} to create
  @param parameters the {@code Object[]} of constructor parameters
  @param <T> the protocol type
  @return T