widgets: Create model of AlbumWidget in a private function

Create model of AlbumWidget in a private function as clearing it causes
crash in Albums view.
Merge pull request #175 from JacksonIsaac/fix144

Create private method for creating model
Added uk translation
view: don't hit tracker every time the user scrolls

Cache the number of items in the fully loaded view the first time
it's needed, and use that value for all future scrolling.

Note: if we ever support watching the library for changes, we need
to invalidate the cache.

https://bugzilla.gnome.org/show_bug.cgi?id=706025
Revert "view: don't hit tracker every time the user scrolls"

This reverts commit 7bf56d19ad0a54c2b8eb1f1591c216424db92cbc.

For some reason, the author was reassigned to me. Reverting this and
pushing a new one with the correct author field.
view: don't hit tracker every time the user scrolls

Cache the number of items in the fully loaded view the first time
it's needed, and use that value for all future scrolling.

Note: if we ever support watching the library for changes, we need
to invalidate the cache.

https://bugzilla.gnome.org/show_bug.cgi?id=706025
widgets: Cache vadjusment in AllArtistsAlbums.
Merge pull request #172 from JacksonIsaac/issue144

widgets: Cache vadjusment in AllArtistsAlbums
Added Slovenian translation
widget: remove call to '_on_scrollbar_visible'

Instead of calling this function. Call the _on_scrolled_win_change
function directly.
Merge pull request #176 from JacksonIsaac/fix114

widget: remove call to '_on_scrollbar_visible'
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