Draft: [#3052574] Facets AJAX

Combine all of the compatible contributions into a working branch to allow easy review and continued work on the issue.

Please "fix conflicts+rebase 2.0.x" instead of merging in 2.0.x to avoid breaking history to a point that automated rebase no longer works.

js/facets-views-ajax.js

@@ -155,7 +155,7 @@
         };
         // replace the current history state so that it is available on popstate when clicking back after first
         window.history.replaceState(view_state, document.title);
-        window.history.pushState(view_state, document.title, window.location.origin + window.location.pathname + url.search);
+        window.history.pushState(view_state, document.title, window.location.origin + url.pathname + url.search);
 
       }