cache cover location in tableview
add the coverlocation in the temporaryview of the database. With
this we can avoid having to do db queries when 'loadCoverArt' is emitted
from a tableview. (thanks kain88)
Initial refactoring - loading covers from coverLocation and trackId instead of using TIO.

Using TIO requeries a lot of unnecessary information for coverart stuff
and it can make the loading/searching process slower when the user
request a lot of pixmaps at the same time.
Using pixmapFound(int trackId, QPixmap cover) instead of pixmapFound(QString coverLocation, QPixmap cover)
Moving TIO::parseCoverArt() to coverart class
Removing get/set coverartlocation from TIO
Moving all coverart class to coverartdao
it also remove the coverart class