Added 'role' attribute to hidden tag fields of payment service form.

Without this change it's not possible to programmatically find these input elements by Javascript integration-independently because fields like "order" will have other actual names as set by particular service mappings.

With this patch "order" input for example for Paysbuy integration will be:

    <input id="inv" name="inv" role="payment-form-order" type="hidden" value="42">

So I can query it with

    $("[role='payment-form-order']")

without having to know particular input name.

More info on "role" html attribute http://www.w3.org/TR/role-attribute/