Fix unregistered dois

* Adds a curation task (datacitexmlvalidator) to validate Dryad-generated DataCite XML against DataCite schema 2.2
* Fixes error that prevented DOIs from being registered during DOIDbSync syncall
* In syncall, verifies that item is in blackout or archived dryad data package or file.

See [Trello 113](https://trello.com/c/QQfVsDR3)