Support subtitle offset

MediaBrowser.Controller/Entities/Audio/Audio.cs

@@ -7,7 +7,6 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Runtime.Serialization;
-using System.Threading;
 
 namespace MediaBrowser.Controller.Entities.Audio
 {
@@ -15,7 +14,6 @@ namespace MediaBrowser.Controller.Entities.Audio
     /// Class Audio
     /// </summary>
     public class Audio : BaseItem, 
-        IHasMediaStreams, 
         IHasAlbumArtist, 
         IHasArtist, 
         IHasMusicGenres, 

MediaBrowser.Controller/Entities/IHasMediaStreams.cs

@@ -1,10 +0,0 @@
-
-namespace MediaBrowser.Controller.Entities
-{
-    /// <summary>
-    /// This is essentially a marker interface
-    /// </summary>
-    public interface IHasMediaStreams
-    {
-    }
-}

MediaBrowser.Controller/Entities/Video.cs

@@ -20,7 +20,6 @@ namespace MediaBrowser.Controller.Entities
     /// Class Video
     /// </summary>
     public class Video : BaseItem, 
-        IHasMediaStreams, 
         IHasAspectRatio, 
         IHasTags, 
         ISupportsPlaceHolders,