Prefer artist over album artist.

E.g. when playing a compilation title, one very likely wants to see the real
artist instead of 'Various artists'.

Change-Id: Id8ccf655ed0e0a21a5b67e0a6d0fef5a7fad6415
Allow adjusting progress on touch events.

Change-Id: I3c9c7364a92b1d0f5ab61321fd16eba242c1e6ff