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/dialogs/organisedialog.cpp

@@ -96,7 +96,8 @@ OrganiseDialog::OrganiseDialog(TaskManager *task_manager, QWidget *parent)
   tags[tr("Comment")] = "comment";
   tags[tr("Length")] = "length";
   tags[tr("Bitrate", "Refers to bitrate in file organise dialog.")] = "bitrate";
-  tags[tr("Samplerate")] = "samplerate";
+  tags[tr("Sample rate")] = "samplerate";
+  tags[tr("Bit depth")] = "bitdepth";
   tags[tr("File extension")] = "extension";
 
   // Naming scheme input field