New video transcoder (#27)

* New video transcoder

* Set a smaller max muxing size + logging tweaks

* No need to return an err since it wiill panic anyway

* Use a default encoder preset if one is not supplied

* Rename to NewTranscoder.  Add comments.

* Rename Bitrate to VideoBitrate. Config file changes required with this rename.

* Allow overrides of segment length. Allow offline stream to live in a single segment

* Append offline state video to existin HLS stream instead of overwriting because players do not like that

* Make properties private as they do not need to be exported

core/status.go

@@ -47,7 +47,5 @@ func SetStreamAsDisconnected() {
 	_stats.StreamConnected = false
 	_stats.LastDisconnectTime = time.Now()
 
-	if config.Config.EnableOfflineImage {
-		ffmpeg.ShowStreamOfflineState()
-	}
+	ffmpeg.ShowStreamOfflineState()
 }