Added initial methods for getting groups, hosts apps and items.

plugins/datasource-zabbix/zabbixCacheSrv.js

@@ -34,10 +34,22 @@ function (angular, _) {
 
     var p = ZabbixCache.prototype;
 
+    p.getGroups = function() {
+      return this._groups;
+    };
+
     p.getHosts = function() {
       return this._hosts;
     };
 
+    p.getApplications = function() {
+      return this._applications;
+    };
+
+    p.getItems = function() {
+      return this._items;
+    };
+
     /**
      * Group Zabbix applications by name
      * @param  {[type]} applications [description]