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/alsadevicefinder.cpp

@@ -35,8 +35,7 @@
 #include "alsadevicefinder.h"
 
 AlsaDeviceFinder::AlsaDeviceFinder()
-    : DeviceFinder("alsa", "alsasink") {
-
+    : DeviceFinder("alsa", {"alsa","alsasink"}) {
 }
 
 QList<DeviceFinder::Device> AlsaDeviceFinder::ListDevices() {