Implement IJsonSerializable, BeatmapInfo IJsonSerializable.

osu.Game/IO/Serialization/IJsonSerializable.cs

@@ -0,0 +1,29 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using Newtonsoft.Json;
+
+namespace osu.Game.IO.Serialization
+{
+    public interface IJsonSerializable
+    {
+    }
+
+    public static class JsonSerializableExtensions
+    {
+        public static string Serialize(this IJsonSerializable obj)
+        {
+            return JsonConvert.SerializeObject(obj);
+        }
+
+        public static T Deserialize<T>(string objString)
+        {
+            return JsonConvert.DeserializeObject<T>(objString);
+        }
+
+        public static T DeepClone<T>(this IJsonSerializable obj)
+        {
+            return Deserialize<T>(Serialize(obj));
+        }
+    }
+}