Add better screen hierarchy and placeholder for dev build disclaimer.

osu.Game/Screens/Loader.cs

@@ -0,0 +1,28 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using osu.Framework.Allocation;
+using osu.Framework.Screens;
+using osu.Game.Screens.Menu;
+
+namespace osu.Game.Screens
+{
+    class Loader : OsuScreen
+    {
+        internal override bool ShowOverlays => false;
+
+        public Loader()
+        {
+            ValidForResume = false;
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(OsuGame game)
+        {
+            if (game.IsDeployedBuild)
+                new Disclaimer().Preload(game, d => Push((Screen)d));
+            else
+                new Intro().Preload(game, d => Push((Screen)d));
+        }
+    }
+}