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/core.go

@@ -51,7 +51,9 @@ func createInitialOfflineState() error {
 		}
 	}
 
-	return ffmpeg.ShowStreamOfflineState()
+	ffmpeg.ShowStreamOfflineState()
+
+	return nil
 }
 
 func resetDirectories() {