public async Task<User> CreateUser(string username, string pass, string email)
        {
            try
            {
                var user = new ParseUser()
                {
                    Username = username,
                    Password = pass,
                    Email = email
                };

                User createdUser = new User()
                {
                    Username = user.Username
                };

                await user.SignUpAsync();

                await ParseUser.LogInAsync(username, pass);
                ((App)App.Current).AuthenticatedUser = ParseUser.CurrentUser;

                return createdUser;
            }
            catch (Exception e)
            {
                new MessageDialog(e.Message).ShowAsync();
                return null;
            }
        }
        public async Task<User> Login(string username, string pass)
        {
            try
            {
                await ParseUser.LogInAsync(username, pass);
                var currentUser = ParseUser.CurrentUser;
                User createdUser = new User()
                {
                    Username = currentUser.Username
                };

                ((App)App.Current).AuthenticatedUser = currentUser;

                return createdUser;
            }
            catch (Exception e)
            {
                new MessageDialog("Грешно потребителско име или парола.").ShowAsync();
                return null;
            }
        }