GUI: display error stack trace in error page

dream/platform/src/dream/index.html

@@ -39,6 +39,8 @@
       <a href="javascript: location.reload()">Click here to reload the page</a><br/>
       The error detail is:
       <pre>{{error}}</pre>
+      <br/>Stack Trace is:
+      <pre>{{error_stack}}</pre>
     </script>
 
   </head>

dream/platform/src/dream/index.js

@@ -436,7 +436,7 @@
           }
           console.error(error.stack);
           document.querySelector("article[class='gadget_container']")
-            .innerHTML = error_template({ error: error });
+            .innerHTML = error_template({ error: error, error_stack: error.stack});
         });
     });
 }(window, jQuery, rJS, RSVP, Handlebars, initGadgetMixin));