add setting to control transcodng throttle

MediaBrowser.Model/Configuration/EncodingOptions.cs

@@ -8,12 +8,16 @@ namespace MediaBrowser.Model.Configuration
         public double DownMixAudioBoost { get; set; }
         public string H264Encoder { get; set; }
         public bool EnableDebugLogging { get; set; }
+        public bool EnableThrottling { get; set; }
+        public int ThrottleThresholdSeconds { get; set; }
 
         public EncodingOptions()
         {
             H264Encoder = "libx264";
             DownMixAudioBoost = 2;
             EncodingQuality = EncodingQuality.Auto;
+            EnableThrottling = true;
+            ThrottleThresholdSeconds = 120;
         }
     }
 }