Fix data model to properly create FKs + fields

The issue before was that fields weren't properly generating FK fields in the downstream entities. This resolves those issues and also takes care of cascade deletion of orphaned data on removal requests through the API. Deleting through direct SQL needs more care as you need to cascade, but the normal case will be to manage through the API.

The tack on is that we more closely follow recommended usage of hibernate by managing FK through entity references now.

Added the Releng folks as its Java code, but its essentially fields and annotations rather than actual logic.