Check all images imported successfully

[govekk]

Currently, if imports break partway through, the log file in Dropbox will just list "Successfully imported" for those images but nothing for the un-imported images. However, because all images are copied onto the server first, this makes it difficult to catch imports that fail on the OMERO side.

It would be nice to send some message to the log file for errors in the OMERO import, or do a check at the end that all images listed in the spreadsheet now exist on the OMERO server.