mysql-connector: imlement getTrends()

dist/datasource-zabbix/zabbix.js

@@ -68,6 +68,7 @@ System.register(['angular', 'lodash', './utils', './zabbixAPI.service.js', './za
         if (enableDirectDBConnection) {
           this.dbConnector = new ZabbixDBConnector(sqlDatasourceId);
           this.getHistory = this.dbConnector.getHistory.bind(this.dbConnector);
+          this.getTrend = this.dbConnector.getTrends.bind(this.dbConnector);
         }
       }