query: Sort albums by their title

The album variable in the query is redefined, so we should use the title
variable instead. Also, convert the title to lower case first before sorting.

https://bugzilla.gnome.org/show_bug.cgi?id=705093
query: Sort album tracks by their album disc number

https://bugzilla.gnome.org/show_bug.cgi?id=705038
query: Sort artist names case insensitively

https://bugzilla.gnome.org/show_bug.cgi?id=706242
Merge pull request #177 from gnome-prototypes-team/fix-item-order

Fix sorting of items