Move UMG importers to extensions.

Assets/Cryville/Crtr/Extensions/Umg/Extension.cs

@@ -0,0 +1,18 @@
+using Cryville.Crtr.Extension;
+using System.Collections.Generic;
+
+namespace Cryville.Crtr.Extensions.Umg {
+	public class Extension : ExtensionInterface {
+		public override IEnumerable<ResourceConverter> GetResourceConverters() {
+			return new ResourceConverter[] {
+				new ChartResourceImporter(),
+				new RulesetResourceImporter(),
+				new SkinResourceImporter(),
+			};
+		}
+
+		public override IEnumerable<LocalResourceFinder> GetResourceFinders() {
+			return null;
+		}
+	}
+}