*8997* Dataverse plugin: add field for dataset description to suppfile form

Add field for authors to describe dataset submitted with article. If no description provided, map article abstract to dataset description.
*8997* Dataverse plugin: add contributor/sponsoring agency to dataset metadata

Map sponsors, contributing agencies in article & suppfile metadata to dataset as contributor funders.
Filter repeated values in article & suppfile metadata (subjects, types, or contributors) mapped to single dataset field.
*8997* Dataverse plugin: add author affiliation to dataset metadata
Merge pull request #351 from jwhitney/8997

*8997* Support new metadata fields added to Dataverse data deposit API