Managed repository template path expansions

Documents managed repository template path expansion terms, accompanying https://github.com/openmicroscopy/openmicroscopy/pull/2701. These changes are staged at http://www.openmicroscopy.org/site/support/omero5-staging/sysadmins/fs-upload-configuration.html.
NB: for this and date/time entries, I almost wonder if we would be better put to explicitly use `String.format()` and `SimpleDateFormat.format()` sub-languages.