#7 multitrack flles not handled correctly

[chrysn]

for multitrack flac files, mpd sends out more than one "Title" and "Artist"
reply -- according to http://www.musicpd.org/mantis/view.php?id=2748, this
is not a bug on their side.

gbemol only displays the first of the responses, which results in the whole
album having the album name as track title.