Introduce the concept of SkinComponents

Removes reliance on string lookups and better defines elements for introduction into database

osu.Game.Rulesets.Osu/OsuSkinComponent.cs

@@ -0,0 +1,19 @@
+// 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.Game.Skinning;
+
+namespace osu.Game.Rulesets.Osu
+{
+    public class OsuSkinComponent : PlaySkinComponent<OsuSkinComponents>
+    {
+        public OsuSkinComponent(OsuSkinComponents component)
+            : base(component)
+        {
+        }
+
+        protected override string RulesetPrefix => OsuRuleset.SHORT_NAME;
+
+        protected override string ComponentName => Component.ToString().ToLower();
+    }
+}