Changed id for payment_method_$gateway from <input> to <li>

Changed CSS ID for payment_method_$gateway from radio button to <li> container. This allows to apply custom CSS style for all elements of gateways. And not only to radio button (that has no sense).
Merge pull request #3976 from samuelaguilera/master

Changed id for payment_method_$gateway from <input> to <li>