Fix 817 (#851)

* problems: update panel schema

* update packages (build with node 12)

* problems: use datasource from target

* problems: fix query editor after schema update

* problems: fix list layout

* update circleci node image to 12

* fix tests

src/panel-triggers/utils.ts

@@ -1,4 +1,6 @@
+import _ from 'lodash';
 import moment from 'moment';
+import { DataQuery } from '@grafana/ui/';
 import * as utils from '../datasource-zabbix/utils';
 import { ZBXTrigger } from './types';
 
@@ -20,3 +22,13 @@ export function formatLastChange(lastchangeUnix: number, customFormat?: string)
   const lastchange = timestamp.format(format);
   return lastchange;
 }
+
+export const getNextRefIdChar = (queries: DataQuery[]): string => {
+  const letters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
+
+  return _.find(letters, refId => {
+    return _.every(queries, other => {
+      return other.refId !== refId;
+    });
+  });
+};