move %time% template expansion term to only user-owned (rebased from dev_5_0)

Documents changes by https://github.com/openmicroscopy/openmicroscopy/pull/2792 and is staged at http://www.openmicroscopy.org/site/support/omero5.1-staging/sysadmins/fs-upload-configuration.html.

--rebased-from #860