Update v1.4

- replaced default icon in coverflow view with a HQ .svg instead of
previous .png, thanks Oleg and Teoman for your help with that
- big thanks to Tomoms for his bug report, now BelleXdefault isn't
BelleXwhite
- removed a few useless Qt/C++ imports
- added a few more comments to code
- added option to enable/disable fullscreen
- moved a bit code from QtQuick to Qt