add custom channel stream selector system (#2076)

* add some basic channel stream selector models

* change windows ffmpeg url

* implement basic stream selection

* fixes

ErsatzTV.Core/Interfaces/Metadata/ILocalFileSystem.cs

@@ -14,4 +14,5 @@ public interface ILocalFileSystem
     bool FolderExists(string folder);
     Task<Either<BaseError, Unit>> CopyFile(string source, string destination);
     Unit EmptyFolder(string folder);
+    Task<string> ReadAllText(string path);
 }