DS-2119. EZID IdentifierProvider Metadata Mapping.

Added DataCite XML based metadata mapping option for EZIDIdentifierProvider module

https://jira.duraspace.org/browse/DS-2119
The DataCite XML format cannot be used with the EZID provider, because one of the DataCite mandatory properties cannot be supplied:  the identifier itself is assigned by EZID and will not be known until after registration.