Separate extension classes into external assembly.

Assets/Cryville/Crtr/Browsing/ResourceBrowserMaster.cs

@@ -1,7 +1,7 @@
 using Cryville.Common;
 using Cryville.Common.Unity.UI;
 using Cryville.Crtr.Config;
-using Newtonsoft.Json;
+using Cryville.Crtr.Extension;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.SceneManagement;
@@ -94,24 +94,4 @@ namespace Cryville.Crtr.Browsing {
 		public AsyncDelivery<Texture2D> Cover { get; set; }
 		public ChartMeta Meta { get; set; }
 	}
-
-#pragma warning disable IDE1006
-	public class MetaInfo {
-		public string name { get; set; }
-		public string author { get; set; }
-		[JsonRequired]
-		public string data { get; set; }
-	}
-	public class SongMetaInfo {
-		public string name { get; set; }
-		public string author { get; set; }
-	}
-	public class ChartMeta : MetaInfo {
-		public SongMetaInfo song { get; set; }
-		public float length { get; set; }
-		public string ruleset { get; set; }
-		public int note_count { get; set; }
-		public string cover { get; set; }
-	}
-#pragma warning restore IDE1006
 }