fix #11965: join images to plate runs for leaf queries

Fixes http://trac.openmicroscopy.org.uk/ome/ticket/11965.
Given plates with runs, a script like that in http://trac.openmicroscopy.org.uk/ome/ticket/11965#comment:6 should now return objects in `ps` that have the well sample images loaded. Should also work for screens with plates with runs.