Core: Clean up FileIconProvider interface

Change-Id: I98c3c8796cb887f5bb3c5184854562ff36727836
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
Utils: Remove dead code

Change-Id: I9e9c7192308630fd85c4ff49120f34dbc8b0c724
Reviewed-by: hjk <hjk121@nokiamail.com>