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

ext/libstrawberry-common/core/logging.cpp

@@ -44,6 +44,7 @@ static Level sDefaultLevel = Level_Debug;
 static QMap<QString, Level>* sClassLevels = nullptr;
 static QIODevice *sNullDevice = nullptr;
 
+//const char* kDefaultLogLevels = "*:3";
 const char* kDefaultLogLevels = "GstEnginePipeline:2,*:3";
 
 static const char *kMessageHandlerMagic = "__logging_message__";