plone.app.widgets support: Let the z3c.form widget's get_start_field method prefer 'name' attribute over the 'id' attribute. Looks like, with plone.app.widgets the rendered input field doesn't have an 'id' attribute any more. Also, integrate lates changes from jquery.recurrenceinput.js, which also handles 'name' attributes when trying to get the start field from the surrounding form.