fix #12495: have Insight report image import date correctly (rebased from dev_5_0)

Check that when you click on an image in Insight, the metadata panel reports the correct import time. Change the image name, log out then back in, then check that the import time remains unaltered.

Fixes http://trac.openmicroscopy.org.uk/ome/ticket/12495.
--rebased-from #2869