corrected wrong json format in dump file

sw/lib/configuration.dart

@@ -53,7 +53,8 @@ class _MyHomePageState extends State<Configuration> {
       String filepath = join(directory.path, filename);
 
       final File file = File(filepath);
-      await file.writeAsString(eventsJson);
+      String dumpStr = "{\"events\":" + eventsJson + "}";
+      await file.writeAsString(dumpStr);
       debugPrint('Stored file at: ' + filepath);
 
       setState(() {});

sw/lib/databaseconnector.dart

@@ -125,12 +125,14 @@ abstract class DatabaseConnector{
   // Create a json readable event dump
   Future<String> eventDump() async {
     List<Event> events = await getEvents();
-    String ev = '[';
+    var ev = '[';
     for (var event in events) {
       ev += jsonEncode(event);
       ev += ',';
     }
+    ev = ev.substring(0, ev.length - 1); // Remove last ,
     ev += ']';
     return ev;
+
   }
 }