code: @SuppressWarnings("unchecked")
    public <L extends List> L setListProperty(final L list,
                                              final String name,
                                              final String val) {
      removeProperty(list, name);
      return addListProperty(list, name, val);
    }
docs: Set a property
  
  @param list the list - possibly null
  @param name of property
  @param val of property
  @return possibly newly created list