Added central user credentials management

lib/storage/base/settingsProvider.dart

@@ -1,9 +1,9 @@
 import 'dart:convert';
 import 'dart:developer';
 import 'package:flutter/material.dart';
-import 'package:marianum_mobile/storage/file/fileSettings.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
+import '../file/fileSettings.dart';
 import '../gradeAverages/gradeAveragesSettings.dart';
 import '../talk/talkSettings.dart';
 import '../timetable/timetableSettings.dart';