ext5migrate: use 'refresh' event to reload components using DiffStore

'datachanged' event was not reloading the store with ExtJS5,
but 'refresh' does.
According to the API description 'refresh' seems to be what we need:
http://docs.sencha.com/extjs/5.1/5.1.0-apidocs/#!/api/Ext.data.AbstractStore-event-refresh

www/manager5/data/DiffStore.js

@@ -78,7 +78,7 @@ Ext.define('PVE.data.DiffStore', {
 	    first_load = false;
 
 	    me.resumeEvents();
-	    me.fireEvent('datachanged', me);
+	    me.fireEvent('refresh', me);
 	});
     }
 });