Improve support for embedded metadata; support external subtitles with strm files

MediaBrowser.Controller/LiveTv/ITunerHost.cs

@@ -46,6 +46,10 @@ namespace MediaBrowser.Controller.LiveTv
         Task<List<MediaSourceInfo>> GetChannelStreamMediaSources(string channelId, CancellationToken cancellationToken);
 
         Task<List<TunerHostInfo>> DiscoverDevices(int discoveryDurationMs, CancellationToken cancellationToken);
+        bool IsSupported
+        {
+            get;
+        }
     }
     public interface IConfigurableTunerHost
     {