Lots of code refactoring to use XAML behaviors instead of code-behind

New Save button in the AppBar
EntryPage now uses the same AppBar as GroupPage (but not shared...)
Some new Symbol mappings

ModernKeePass/Common/MessageDialogHelper.cs

@@ -0,0 +1,35 @@
+using System;
+using Windows.UI.Popups;
+using Windows.UI.Xaml.Controls;
+using ModernKeePass.Interfaces;
+using ModernKeePass.ViewModels;
+
+namespace ModernKeePass.Common
+{
+    public static class MessageDialogHelper
+    {
+        public static async void ShowDeleteConfirmationDialog(string text, IPwEntity model, Frame backFrame)
+        {
+            // Create the message dialog and set its content
+            var messageDialog = new MessageDialog(text);
+
+            // Add commands and set their callbacks; both buttons use the same callback function instead of inline event handlers
+            messageDialog.Commands.Add(new UICommand("Delete", delete =>
+            {
+                ToastNotificationHelper.ShowUndoToast(model);
+                model.MarkForDelete();
+                if (backFrame.CanGoBack) backFrame.GoBack();
+            }));
+            messageDialog.Commands.Add(new UICommand("Cancel"));
+
+            // Set the command that will be invoked by default
+            messageDialog.DefaultCommandIndex = 1;
+
+            // Set the command to be invoked when escape is pressed
+            messageDialog.CancelCommandIndex = 1;
+
+            // Show the message dialog
+            await messageDialog.ShowAsync();
+        }
+    }
+}