Implement session locking with --lock-session option

static/css/app.css

@@ -475,6 +475,7 @@
   position: fixed;
   right: 8px;
   top: 10px;
+  display: none;
 }
 
 #edit_connection, #close_connection {

static/js/app.js

@@ -1080,6 +1080,10 @@ $(document).ready(function() {
 
       $("#current_database").text(resp.current_database);
       $("#main").show();
+
+      if (!resp.session_lock) {
+        $(".connection-actions").show();
+      }
     }
   });
 });