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/Interfaces/IPwEntity.cs

@@ -13,5 +13,7 @@ namespace ModernKeePass.Interfaces
 
         void CommitDelete();
         void UndoDelete();
+        void Save();
+        void MarkForDelete();
     }
 }