add hls segmenter streaming mode (#400)

* hls segmenter wip

* log message

* close unused transcode sessions after 2 minutes

* use frame rate for 2s keyframes in hls segmenter

* add frame rate to media version

* fix segmenter framerate calculation

* automatically restart hls segmenter with next scheduled item

* cleanup

* update changelog

* decrease segmenter start delay

ErsatzTV.Core/Metadata/LocalFileSystem.cs

@@ -56,5 +56,20 @@ namespace ErsatzTV.Core.Metadata
                 return BaseError.New(ex.ToString());
             }
         }
+
+        public Unit EmptyFolder(string folder)
+        {
+            foreach (string file in Directory.GetFiles(folder))
+            {
+                File.Delete(file);
+            }
+
+            foreach (string directory in Directory.GetDirectories(folder))
+            {
+                Directory.Delete(directory, true);
+            }
+
+            return Unit.Default;
+        }
     }
 }