Feature request: Make links that have children also navigable #15

Currently, a link that has children is assumed to be a dummy link that doesn't actually need to link to a page. Clicking it only shows its child items, and doesn't provide a way to actually navigate to that page.

CMSs such as Drupal build menus out of pieces of content and don't make heavy use of dummy links such as are expected by RMLM. To solve this, an option should be added to add a navigable link to an item at the top of its child link list.