code: public AppHelper add(String name, String displayValue, String description, Object defaultValue)
      {
          add(name, displayValue, description, defaultValue.toString());
          return this;
      }
docs: Adds an argument to this application helper.
  
  @param name the (case-sensitive) argument name.
  @param displayValue the display value to be shown in the usage print-out for this argument.  For instance, a number or specific expected format.
  @param description the description for the argument to be displayed in the usage print-out.
  @param defaultValue the default value (as an Object) to be used for an optional argument.  If no default value is provided, the argument will be required in the command line call.
  @return reference to this application helper, allowing command-chaining.