code: @Nonnull
    public static EInterrupt shutdownAndWaitUntilAllTasksAreFinished (@Nonnull final ExecutorService aES)
    {
      return shutdownAndWaitUntilAllTasksAreFinished (aES, 1, TimeUnit.SECONDS);
    }
docs: Call shutdown on the {@link ExecutorService} and wait indefinitely until it
  terminated.
  
  @param aES
  The {@link ExecutorService} to operate on. May not be
  <code>null</code>.
  @return {@link EInterrupt#INTERRUPTED} if the executor service was
  interrupted while awaiting termination. Never <code>null</code>.