Upgraded Protobuf, and added api support for it

MediaBrowser.Model/DTO/AudioInfo.cs

@@ -1,13 +1,23 @@
-
+using ProtoBuf;
+
 namespace MediaBrowser.Model.DTO
 {
+    [ProtoContract]
     public class AudioInfo
     {
+        [ProtoMember(1)]
         public int BitRate { get; set; }
+
+        [ProtoMember(2)]
         public int Channels { get; set; }
 
+        [ProtoMember(3)]
         public string Artist { get; set; }
+
+        [ProtoMember(4)]
         public string Album { get; set; }
+
+        [ProtoMember(5)]
         public string AlbumArtist { get; set; }
     }
 }