Add ability to remove ul tag from wp_nav_menu result

[spangborn]

The new (and awesome) wp_nav_menu() function provides the ability to remove the "container" ( the DIV that wraps around the entire result), but you can't remove the UL that wraps the list items at present to only produce the list items. It'd be really awesome if it were possible to remove the UL tags, as it would enable theme designers/developers to use the new wp_nav_menu() inside of pre-existing UL's for things like inline navigation menus on the top of a page.

I agree, and I think the way to do it is to be able to pass element patterns. So for example something like this, perhaps:

$args = array(
   'items_wrap' => '<ul id="%1$s" class="%2$">%3$s</ul>',
);
wp_nav_menu( $args );

(In [16519]) Introduce items_wrap arg to wp_nav_menu(). props filosofo, fixes #14235.

(In [16520]) Escape the wrap ID and class attributes going into sprintf() and s/slug/wrap_id/ to make it more obvious. see #14235.