Generic macro for displaying vertical navigation menus

#verticalNavigation($menu $options)

 * $menu = vector of items
 * item = map with the following fields:
 *        'id'       : mandatory
 *        'name'     : the text displayed for the corresponding menu item;
 *                     optional, defaults to
 *                     $msg.get("$!{translationPrefix}${item.id}")
 *        'url'      : the "action" of the menu item; optional
 *        'cssClass' : a specific css class for the menu item for custom
 *                     styling; optional, defaults to ''
 *        'children' : vector of items, allowing to recursively define submenus
 *
 * @param $menu the menu object, in the format described above
 * @param $options a map of options, where the following entries are currently used:
 *        'translationPrefix' :  the translation prefix added to the id of each
 *                     item, in order to generate the name; ignored for items whose
 *                     name is specified
 *        'crtItemId': identifier of the current menu item (for differential styling)
 *        'cssClass' : specific css class for this menu