plugins: added backward compatible path for rxjs

public/app/features/plugins/plugin_loader.ts

@@ -64,16 +64,21 @@ exposeToPlugin('lodash', _);
 exposeToPlugin('moment', moment);
 exposeToPlugin('jquery', jquery);
 exposeToPlugin('angular', angular);
+exposeToPlugin('d3', d3);
 exposeToPlugin('rxjs/Subject', Subject);
 exposeToPlugin('rxjs/Observable', Observable);
-exposeToPlugin('d3', d3);
+
+// backward compatible path
+exposeToPlugin('vendor/npm/rxjs/Rx', {
+  Subject: Subject,
+  Observable: Observable
+});
 
 exposeToPlugin('app/features/dashboard/impression_store', {
   impressions: impressions,
   __esModule: true
 });
 
-
 exposeToPlugin('app/plugins/sdk', sdk);
 exposeToPlugin('app/core/utils/datemath', datemath);
 exposeToPlugin('app/core/utils/file_export', fileExport);