* Added TomahawkUtils::tinted(QPixmap, QColor).
 Use tinted convenience method in ImageRegistry.
* Tint header images.
* If no source avatar is avail, return big tinted default collection image for collection's bigIcon.
* Tint default FlexibleTreeView's pixmap.
* Default TreeModel icon is now the collection image.
* BasicHeader can tint its pixmaps.