GUACAMOLE-723: Move getClientIdentifier() to GroupListItem for convenience of other uses of the guacGroupList directive.

guacamole/src/main/webapp/app/home/templates/connectionGroup.html

@@ -1,4 +1,4 @@
 <span class="home-connection-group name">
-    <a ng-show="item.balancing" ng-href="#/client/{{context.getClientIdentifier(item)}}">{{item.name}}</a>
+    <a ng-show="item.balancing" ng-href="#/client/{{ getClientIdentifier() }}">{{item.name}}</a>
     <span ng-show="!item.balancing">{{item.name}}</span>
 </span>