Re-enabled write mode in KeePassLib

Set database as part of App (so, Singleton)
Changed main page view model
WIP and testing saving mechanism

ModernKeePass/ViewModels/DatabaseVm.cs

@@ -1,69 +0,0 @@
-using System.ComponentModel;
-using Windows.Storage;
-
-using ModernKeePassLib;
-using ModernKeePassLib.Keys;
-using ModernKeePassLib.Serialization;
-using ModernKeePassLib.Interfaces;
-using Windows.UI.Xaml;
-using System;
-
-namespace ModernKeePass.ViewModels
-{
-    public class DatabaseVm : INotifyPropertyChanged
-    {
-        private PwDatabase database = new PwDatabase();
-        private StorageFile databaseFile;
-
-        public string Password { get; set; }
-        public bool IsOpen { get; set; }
-        public Visibility Visibility { get; private set; }
-        public string ErrorMessage { get; set; }
-        public string Name { get; set; }
-        public GroupVm RootGroup { get; set; }
-
-
-        public DatabaseVm()
-        {
-            Visibility = Visibility.Collapsed;
-        }
-        public DatabaseVm(StorageFile databaseFile)
-        {
-            this.databaseFile = databaseFile;
-            Visibility = Visibility.Visible;
-        }
-        public async void Open()
-        {
-            var key = new CompositeKey();
-            try
-            {
-                key.AddUserKey(new KcpPassword(Password));
-                await database.Open(IOConnectionInfo.FromFile(databaseFile), key, new NullStatusLogger());
-                IsOpen = database.IsOpen;
-                Name = databaseFile.DisplayName;
-                RootGroup = new GroupVm (database.RootGroup);
-            }
-            catch (ArgumentNullException)
-            {
-                ErrorMessage = "Password cannot be empty";
-                NotifyPropertyChanged("ErrorMessage");
-            }
-            catch (InvalidCompositeKeyException)
-            {
-                ErrorMessage = "Wrong password";
-                NotifyPropertyChanged("ErrorMessage");
-            }
-            finally
-            {
-                // TODO: move this when implementing write mode
-                database.Close();
-            }
-        }
-
-        public event PropertyChangedEventHandler PropertyChanged;
-        public void NotifyPropertyChanged(string propertyName)
-        {
-            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
-        }
-    }
-}