Fix sort order of Submission Part Tab

[aolley]

The submission parts can don't always apply in the same order they have been created because there isn't a part number to sort them by, and without a order by clause, the DB is not guaranteed to return the records in any specific order.

Previously in Turnitintool v1, the submissions tabs were ordered by first to last created, so this change mimics that.

[jmcgettrick]

I can't merge this in as the repositories have now been split but the change has been committed at: https://github.com/jmcgettrick/moodle-mod_turnitintooltwo/commit/28b09d5f0b72dedbdd1d9028924d84e69f67eaae

Thanks