[756] Page furniture development. Carefully aiming to match CKAN's output.

Problems addressed:

* Constrain footer content to strictly be the output of dguk_get_footer_menu so CKAN can have parity.
* Outermost footer div should not be within a .container
* "Log In" and "Sign Up" buttons at the top do not work
* Page state should detect whether user is logged in & render username appropriately
* Clicking main logo does not work (should link to "/")
* Bootstrap's JS is 404ing. Should be using vendor.min.js.
* Pull jQuery from a CDN using the precise markup that CKAN does.
* Navbar no longer appears when clicking "show nav" button (narrow mode)