Menu: load secondary menu in main menu panel

If #wb-sec exists in the DOM, it is prepended to the #wb-sm
panel menu once the menu as finished loading (loaded.wb-menu event).
Menu: virtual click handling of menu items

Allows menus with hidden subment items to be opened on
virtual click (triggers onHoverFocus processing).
Merge pull request #3504 from patheard/wb-sec

Secondary menu and mobile view