We do not rescan for duplicates if an image is deleted any more.

Instead, all duplicates albums in left pane are updated, i.e. the items count,
and average similarity are recalculated. If only one duplicate is left,
the duplicates album is hidden. This solves the problem of losing context
due to the rebuild of the SAlbums. I see no other good technical
possibility of preserving the context since the SAlbums are deleted automatically.
Also, the similarities to images are not deleted any more. Otherwise the calculation
of the average similarity would be wrong. We will take care of the similarity values
in garbage collection branch.

BUGS: 375573
FIXED-IN: 5.5.0