DS-1745 : Change logic in InstallItem so that dc.date.issued MUST be specified to be set. Add an option to set dc.date.issued="today" to auto-apply today's date. Also add unit tests for new logic
DS-1745 : Backwards compatibility for Initial Questions. If item is "unpublished" and no issued date, set it to today's date.
Merge pull request #373 from tdonohue/DS-1745

DS-1745: DSpace should no longer assign "dc.date.issued=[today]" when date field is missing