This allows methods that return an icon name, to sometimes also
return an icon full path (e.g. because the icon was dynamically generated
and stored into a local cache on disk)
Change-Id: Ib01c3955f4b64236463846241d9814b2d0686634
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>