Clarify data model & data samples to be used for data middleware MVP

[cmharlow]

Task: The goal here is not to limit scope of data models used in future, but to give a clear place for product evolution work to get started. Generate a starting JSON representation indicative of what generally would be transformed from RDF for use in VIVO.

Out of scope: Discussions of RDF ontologies leading to that JSON (except to make a base mapping / crosswalk if and when needed).

Definition of Done:

• JSON specification for some generic data expectations from the data middleware
• Sample data for that JSON
• Persistence store data model for middleware
• API or other data exposure point data model