The image cache is saving images and icon of this images in a sqlite
database. If there are no images they are generated in the backgound.
The icons are fetched by item library.
Task-number: QDS-2782
Task-number: QDS-2783
Task-number: QDS-2858
Change-Id: I5a32cccfef7f8fd8eb78902605a09f5da18ce88e
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>
