Add sorting and ordering on blue and yellow frets

[NeomattGZ]

Small improvement on the current song navigation:

• Red button now goes back to the top of the list if there is no search filter active (allows to get back to the top and select "Random" or "Recommended"
• Yellow button now changes the sort order between song name (default), artist name, and source name.
• Blue button filters on artist if no filter is set, and a second press filters on source instead.

Could be improved:

• Text for navigation menu does not change (I would like to switch it to "Select Source", or "Back to Top")
• Orange button for selecting next section works for song name and artist name, but is broken on source name (it tries to get to the bottom of the list every time, it could be due to the fact that some sources are empty)