Add view system for API JSON responses.

Uses custom view model, strategy, and renderer to render API response
content as JSON, and to convert API response statuses to HTTP codes.
Begin testing abstract entity adapter. Add mock object builder.
Add tests. Remove abstract entity adapter.
Add property API adapter test.
Add value API adapter. Add validations.
make the IsUnique validator association mapping aware.
Add method to resource entities that gets the entity adapter class.
Use validator. Use correct field name.
Merge branch 'develop' into feature/installer
update schema.sql