code: private static <T> Stream<T> streamHelper(IPromise<T>... completedPromises) {
          return Arrays.stream(completedPromises).map(future -> future.get());
      }
docs: helper to stream settled futures unboxed. e.g. all(f1,f2,..).then( farr -> stream(farr).forEach( val -> process(val) );
  Note this can be used only on "settled" or "completed" futures. If one of the futures has been rejected,
  a null value is streamed.
  
  @param completedPromises
  @param <T>
  @return