Update ServeGetAlbumList to reflect @Duncaen's changes

server/ctrlsubsonic/handlers_by_folder.go

@@ -131,7 +131,7 @@ func (c *Controller) ServeGetAlbumList(r *http.Request) *spec.Response {
 	// TODO: think about removing this extra join to count number
 	// of children. it might make sense to store that in the db
 	q.
-		Select("albums.*, count(tracks.id) child_count").
+		Select("albums.*, count(tracks.id) child_count, sum(tracks.length) duration").
 		Joins("LEFT JOIN tracks ON tracks.album_id=albums.id").
 		Group("albums.id").
 		Where("albums.tag_artist_id IS NOT NULL").