Adds navbar with dropdown menus
Navbar placed in header partial, other layouts added.

Controller layouts will use content_for to put relevant content into the
nav bar. The parent bar and the sidebar is no longer rendered on each view.
More layout tweaking, I presume.
Deletes unnecessary files
Unbreaks logged-out root page
Moves parentage/sibling ul to the side of item details.

Deletes the nav bar css (that styled .parent-bar which no longer exists).
The new nav bar is vertical and sits to the left of the item details.
Adds parent thumbnail to parent bar