Show a message when connection to terminal has been lost

www/assets/app.js

@@ -174,6 +174,11 @@
 
         var socket = io({ path: '/sessions/' + sessionId + '/ws' });
 
+        socket.on('instance terminal status', function(name, status) {
+            var instance = $scope.idx[name];
+            instance.status = status;
+        });
+
         socket.on('session ready', function(ready) {
           $scope.setSessionState(ready);
         });

www/index.html

@@ -123,6 +123,7 @@
                                <span>{{uploadMessage}}</span>
                            </div>
                       </div>
+                      <div ng-show="instance.status=='reconnect'" class="uploadStatus">Connection has been lost. Sometimes this happens when a windows instance is joining a swarm. Trying to reconnect terminal...</div>
                       <md-card-content flex id="terminal-{{instance.name}}" class="terminal-container">
                       </md-card-content>
                   </md-card>