This patch is joint work with Simon. The patch introduces the similarity of...

This patch is joint work with Simon. The patch introduces the similarity of images to a specific image
as column in table view. Also, it fixes the sorting by similarity in sketch search.
Moreover, the dysfunctional context menu item "Find duplicates" in people sidebar now leads to the selection
of the people tags as regular tabs in duplicates search. Finally, selecting multiple regular/people tags for
duplicates search is possible. Not to mention some refactoring to make function names more fitting.

BUGS: 374191
CCBUGS: 320666 302923
FIXED-IN: 5.4.0