Open file from Explorer with association works

Major code refactor in Open, Save and Recent pages and VM
Main page automatically opens a sub page depending on context

ModernKeePass/ViewModels/OpenVm.cs

@@ -0,0 +1,50 @@
+using System.ComponentModel;
+using Windows.Storage;
+using Windows.Storage.AccessCache;
+using Windows.UI.Xaml;
+using ModernKeePass.Common;
+
+namespace ModernKeePass.ViewModels
+{
+    public class OpenVm: INotifyPropertyChanged
+    {
+        public bool ShowPasswordBox
+        {
+            get { return ((App) Application.Current).Database.Status == DatabaseHelper.DatabaseStatus.Opening; }
+        }
+
+        public string Name
+        {
+            get { return ((App) Application.Current).Database.Name; }
+        }
+
+        public event PropertyChangedEventHandler PropertyChanged;
+
+        public OpenVm()
+        {
+            var database = ((App) Application.Current).Database;
+            if (database == null || database.Status != DatabaseHelper.DatabaseStatus.Opening) return;
+            OpenFile(database.DatabaseFile);
+        }
+
+        private void NotifyPropertyChanged(string propertyName)
+        {
+            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+        }
+
+        public void OpenFile(StorageFile file)
+        {
+            var database = ((App)Application.Current).Database;
+            database.DatabaseFile = file;
+            NotifyPropertyChanged("Name");
+            NotifyPropertyChanged("ShowPasswordBox");
+            AddToRecentList(file);
+        }
+        
+        private void AddToRecentList(StorageFile file)
+        {
+            var mru = StorageApplicationPermissions.MostRecentlyUsedList;
+            mru.Add(file, file.DisplayName);
+        }
+    }
+}