Add breadcrumb and next/prev page navigation links

We desperately need this for docs.ckan.org - currently when you get to the bottom of a page, there's no link to the next page! You have to scroll back up and pick the next page out of the sidebar. This adds next and prev page links to the bottom of the page. Also adds breadcrumb links to the top of the page.

@teleyinex @rgrp Can one of you merge this?