Refactor skin configuration to be infinitely extensible

osu.Game/Skinning/SkinConfigManager.cs

@@ -0,0 +1,16 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Framework.Configuration;
+
+namespace osu.Game.Skinning
+{
+    public class SkinConfigManager<T> : ConfigManager<T> where T : struct
+    {
+        protected override void PerformLoad()
+        {
+        }
+
+        protected override bool PerformSave() => false;
+    }
+}