Removed the buttonbar partial view.

It no longer had any content, all buttons have been moved to the navbar.
Moved all partials related to the navbar and its buttons to the views/layouts/navbar folder.
Moved user-account-related links in the navbar to a dropdown. Removed the "my feeds" link from navbar.

This way navbar fits into a screen... barely.

Something will have to be done with the "my feeds" link. Perhaps it would be better if the navbar-head link linked with the /feeds path.