Fix extra type differentiation

Change rules for Featurettes and Shorts so they don't both get classed as ExtraType.Clip.

Fix test that these changes break

MediaBrowser.Model/Entities/ExtraType.cs

@@ -13,6 +13,8 @@ namespace MediaBrowser.Model.Entities
         Scene = 6,
         Sample = 7,
         ThemeSong = 8,
-        ThemeVideo = 9
+        ThemeVideo = 9,
+        Featurette = 10,
+        Short = 11
     }
 }