Synchronizer error factory implementation (#645)

* Added sync error factories for outlook and gmail.

* Implement ObjectCannotBeDeletedHandler for OutlookSynchronizer.

* Remove debug code.

* Implement del key to delete on mail list.

* Revert debug code.

Wino.Mail/Views/MailListPage.xaml.cs

@@ -495,4 +495,7 @@ public sealed partial class MailListPage : MailListPageAbstract,
 
     private void SelectAllInvoked(KeyboardAccelerator sender, KeyboardAcceleratorInvokedEventArgs args)
         => MailListView.SelectAllWino();
+
+    private void DeleteAllInvoked(KeyboardAccelerator sender, KeyboardAcceleratorInvokedEventArgs args)
+        => ViewModel.ExecuteMailOperationCommand.Execute(MailOperation.SoftDelete);
 }