Complete transition to schema based metadata

[mark-dce]

ISSUE

We appear to define the same predicates in both
https://github.com/curationexperts/laevigata/blob/master/app/models/etd.rb
https://github.com/curationexperts/laevigata/blob/master/app/models/schemas/emory_etd_schema.rb

This results in warnings like

Same predicate (http://www.ebu.ch/metadata/ontologies/ebucore/ebucore#privateEmailAddress) used for properties post_graduation_email and post_graduation_email
Same predicate (http://purl.org/dc/terms/issued) used for properties graduation_year and graduation_date
Same predicate (http://purl.org/dc/terms/issued) used for properties graduation_date and graduation_date
Same predicate (http://emory.edu/local/hidden) used for properties hidden and hidden

ACCEPTANCE

• All custom attribute <-> predicate mappings are made in the schema
• No duplicate definitions exist in the model