Implement Score Processor Mod Interface

- Add a delegate whenever we want to register an additional fail condition

osu.Game/Rulesets/Mods/IApplicableToScoreProcessor.cs

@@ -0,0 +1,15 @@
+// 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.Game.Rulesets.Scoring;
+
+namespace osu.Game.Rulesets.Mods
+{
+    /// <summary>
+    /// An interface for mods that make general adjustments to score processor.
+    /// </summary>
+    public interface IApplicableToScoreProcessor
+    {
+        void ApplyToScoreProcessor(ScoreProcessor scoreProcessor);
+    }
+}