Summary:
implements the option to sort ascending or descending for all views except the album view.

currently there is only one possibility to sort for each view, e.g. album name for the all album view

Reviewers: #elisa, mgallien

Reviewed By: #elisa, mgallien

Subscribers: mgallien, ngraham

Tags: #elisa

Differential Revision: https://phabricator.kde.org/D12317