Fix setting output/device for Xine and VLC backend

- Fixed setting output and device on Xine and VLC backend
- Fixed track slider for Xine, VLC and Phonon
- Improved backend settings to better support multiple backends
- Added group by samplerate and bitdepth in collection
- Fixed crash on exit when existing instance of the application is already runnung caused by NVIDIA driver
- Changed Q_OS_MAC to Q_OS_MACOS

src/core/mainwindow.cpp

@@ -741,7 +741,6 @@ void MainWindow::ReloadAllSettings() {
   app_->player()->ReloadSettings();
   osd_->ReloadSettings();
   collection_view_->ReloadSettings();
-  app_->player()->engine()->ReloadSettings();
   ui_->playlist->view()->ReloadSettings();
 
 }