Sub-menu items not showing up in Bootstrap3 <768px

[audreyt]

It seems Bootstrap 3 Final adjusted menu styles such that all items are by its own row:

So while the sub-menu from @muan still works in >768px, in "xs" mode (<768px) there are two issues:

1. In desktop, the hovering drops the right-pointing triangles to the middle (should be top);
2. Touch-only devices cannot toggle the expansion of sub-menu items at all:

I wonder if it's easier to reuse Bootstrap 3's $.fn.dropdown for submenus, or adapting something like B3's main menu code is easier.

Custom-coding for this specific fix is good (directly editing index.html to add <script> sections is fine, too). If possible, though, I'd like to see if we can make it into a more generally applicable B3 extension, or adopt one if one exists — that'd be way :cooooooooool: :-)