Made google-play login working again, and fixed numerous bugs

lib/api/webuntis/webuntisApi.dart

@@ -1,7 +1,7 @@
 import 'dart:convert';
 import 'package:http/http.dart' as http;
 
-import '../../model/timetable/endpointData.dart';
+import '../../model/endpointData.dart';
 import '../apiParams.dart';
 import '../apiRequest.dart';
 import '../apiResponse.dart';