Update/Fix of PlayerService when using one or several musics via AddToPlaylistCommand, remote files were not downloaded

UI may use PlayIncomingMusicCommand to play only one music (and also clear playlist, ie. at double-clic on any music in app)
If user select several musics and use a button to push them to playlist, then we must use AddToPlaylistCommand
Merge branch 'master' of https://github.com/SharUTC/SharUTC.git
Merge branch 'master' of https://github.com/SharUTC/SharUTC.git