everywhere: use different session cookie names

If the user is hosting the dashboard in the same domain as
their blog (with a nginx suburi, for example), the two session
cookies clash; logging into one service logs you out of the other.
With this patch, both have separate names.

Fixes https://gitlab.com/commento/commento-ce/issues/49

frontend/js/login.js

@@ -65,7 +65,7 @@
         return;
       }
 
-      global.cookieSet("session", resp.session);
+      global.cookieSet("ownerToken", resp.ownerToken);
       document.location = "/dashboard";
     });
   };