Auto-update playlists (read playlist files)

[gaui]

When importing playlists, it would be awesome to be able to tick an option to make Subsonic read the playlist file straight from the hard-drive. This would be ideal for people that don't use Subsonic for managing their playlist songs.

Similar approach was in Subsonic 4.6, when Subsonic read the playlist file itself. Now when importing, you're only copying the playlist to Subsonic. So after editing your playlist file elsewhere, it doesn't change in Subsonic.

It could be optional to let Subsonic read the playlist file itself when importing playlists.