fix #11877: move import logs to upload jobs instead of annotations

Fixes http://trac.openmicroscopy.org.uk/ome/ticket/11877 to make import logs attached to a fileset's upload job instead of being a file annotation on it; the import log's original file has a distinct MIME type. The upgrade script now includes PL/pgSQL for moving legacy import logs accordingly.

An integration test for the new metadata service method is coming soon.

In testing, make sure that import logs can still be viewed from Insight, and that they indeed no longer exist as annotations in the database.