Added some tests

Removed false first group, replaced it a button in the header
Code refactor

ModernKeePass/ViewModels/Items/SettingsDatabaseVm.cs

@@ -94,6 +94,7 @@ namespace ModernKeePass.ViewModels
         {
             _database = database;
             Groups = _database?.RootGroup.Groups;
+            Groups?.Insert(0, new GroupVm());
         }
     }
 }