[GSoC status report] Week 16

[Téo Mrnjavac]

This week I have finally implemented the sorting GUI as a breadcrumb.
The old testing GUI has been removed. Some graphical glitches might
remain under osx but all in all it works nicely, no major bugs so far.
I also implemented sort order inversion, added shuffle support and
documented the recently added classes.

Today is the soft pencils down date but we still have one week of
GSoC. During this last week I plan to wrap up by adding grouping
support, fixing playlist saving and possibly implementing sort scheme
bookmarks. Actually, the plan is to do whatever needs to be done.