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/HomeVm.cs

@@ -0,0 +1,30 @@
+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 HomeVm : INotifyPropertyChanged
+    {
+        public string Password { get; set; }
+        public Visibility Visibility { get; set; }
+        public string ErrorMessage { get; set; }
+
+        public HomeVm()
+        {
+            Visibility = Visibility.Collapsed;
+        }
+
+        public event PropertyChangedEventHandler PropertyChanged;
+        public void NotifyPropertyChanged(string propertyName)
+        {
+            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+        }
+    }
+}