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/engine/devicefinder.cpp

@@ -23,7 +23,7 @@
 
 #include "devicefinder.h"
 
-DeviceFinder::DeviceFinder(const QString &name, const QString &gstsink): name_(name), gstsink_(gstsink) {
+DeviceFinder::DeviceFinder(const QString &name, const QStringList &outputs): name_(name), outputs_(outputs) {
 }
 
 QString DeviceFinder::GuessIconName(const QString &description) {