Preview feature within maintenance UI

[rhu001]

As well as creating a well formed and fully cited identity, many editors and contributors want to know how an input will display on the HRT. It would be helpful for these users to have access to a preview in HRT feature that would allow them to see how data will appear before publishing.

This was a need that was expressed during SNAC School training held in September, 2017 at the Washington, DC SNAC meeting.