add jsdoc comment to directive params

I think it would be usefull have something like this in template directive

      * 'E'   element             <my-menu></my-menu>
      * 'A'   attribute           <div my-menu></div>
      * 'C'   class               <div class=my-menu></div>
      * 'M'   comment             <!-- directive: my-menu -->

please look at patch
it\`s very small additional but usefull