Allow to block a version of the marketplace

Fix https://github.com/GNS3/gns3-marketplace/issues/10

templates/layout/default.html

@@ -17,6 +17,11 @@
         <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
 
         <script>
+            if (gns3.marketplace_api_version() != 1) {
+                alert("Your client is out of date please update it");
+            }    
+
+
             function gns3_notif(type, msg) {
                 var notif = $("#notif")
                 notif.append("<div class=\"alert alert-" + type + " alert-dismissible fade in\" role=\"alert\"><button type=\"button\" class=\"close\" data-dismiss=\"alert\" aria-label=\"Close\"><span aria-hidden=\"true\">×</span></button>" + msg + "</div>")
@@ -82,5 +87,6 @@
     <div class="container-fluid">
         {% block body %}{% endblock %}
     </div>
+    <small id="powered"></small>
     </body>
 </html>