3.0 Schema review questions remaining

[skyleryoung]

Devin’s points reflect my own assumptions and opinions as well. To emphasize a few key points:

1. In general, I’m in favor of deprecation over deletion.
2. I confirm that location_type exists primarily to delineate virtual locations.
3. I think adding required_document.uri is a good idea. Heuristically, I’m in favor of simply calling it “uri” as that naming convention already exists. However, it’s not a major issue either way.