Make sure all forms have the correct authenticity token

A cached page may include forms, which will then have the wrong
authenticity token, so after the page has finished loading we fix
up those tokens using the one from the meta tags which will always
be correct as we never cache the layout.

app/views/layouts/site.html.erb

@@ -63,7 +63,6 @@
     </script>
 
     <div id="left">
-
       <div id="logo">
         <center>
           <h1><%= t 'layouts.project_name.h1' %></h1>
@@ -125,6 +124,17 @@
         </div>
       </center>
     </div>
+
+    <script type="text/javascript">
+    document.observe("dom:loaded", function () {
+      var auth_token = $$("meta[name=csrf-token]")[0].content;
+
+      $$("form input[name=authenticity_token]").each(function (input) {
+        input.value = auth_token;
+      });
+    }
+    </script>
+
     <% if defined?(PIWIK_LOCATION) and defined?(PIWIK_SITE) -%>
     <%= render :partial => "layouts/piwik" %>
     <% end -%>