Moved application code to the Application layer

Imported Win10 project
Code cleanup
WIP - Use common UWP services for Win8.1 and Win10

ModernKeePass10/Views/MainPageFrames/OpenDatabasePage.xaml.cs

@@ -0,0 +1,58 @@
+using System;
+using Windows.Storage.Pickers;
+using Windows.UI.Xaml;
+using Windows.UI.Xaml.Navigation;
+using ModernKeePass.ViewModels;
+using Windows.Storage.AccessCache;
+using ModernKeePass.Domain.Dtos;
+
+// The Blank Page item template is documented at http://go.microsoft.com/fwlink/?LinkId=234238
+
+namespace ModernKeePass.Views
+{
+    /// <summary>
+    /// An empty page that can be used on its own or navigated to within a Frame.
+    /// </summary>
+    public sealed partial class OpenDatabasePage
+    {
+        public OpenViewModel ViewModel { get; }
+
+        public OpenDatabasePage()
+        {
+            InitializeComponent();
+            ViewModel = new OpenViewModel();
+        }
+
+        protected override async void OnNavigatedTo(NavigationEventArgs e)
+        {
+            base.OnNavigatedTo(e);
+            if (e.Parameter is FileInfo fileInfo)
+            {
+                await ViewModel.OpenFile(fileInfo);
+            }
+        }
+
+        private async void ButtonBase_OnClick(object sender, RoutedEventArgs e)
+        {
+            var picker =
+                new FileOpenPicker
+                {
+                    ViewMode = PickerViewMode.List,
+                    SuggestedStartLocation = PickerLocationId.DocumentsLibrary
+                };
+            picker.FileTypeFilter.Add(".kdbx");
+            
+            // Application now has read/write access to the picked file
+            var file = await picker.PickSingleFileAsync();
+            if (file == null) return;
+
+            var token = StorageApplicationPermissions.FutureAccessList.Add(file);
+            var fileInfo = new FileInfo
+            {
+                Path = token,
+                Name = file.DisplayName
+            };
+            await ViewModel.OpenFile(fileInfo);
+        }
+    }
+}