Hapi-schema

Fixed

- corrected ``admin1.location\_ref`` and ``admin2.admin1\_ref`` to be ``NOT NULL``

Changed

- Switch from sqlite to PostgreSQL

Fixed

- Removed duplicate field sector_code in operational_presence_view
- Add location code back to views

Changed

- removed *_link fields (they can be constructed in the API layer)
- add download_url to resource table
- dataset and resource codes set to VARCHAR(36) (instead of 128)
- column hdx_stub added to dataset table
- rename code to hdx_id in the resource and dataset tables

Fixed

- Specified all foreign key references

Changed

- Table and view names changed to snake case for better compatability
with PostgreSQL

Changed

- Age range: removed description, added integer range
- Dates: renamed to "reference_period", added "start" and
"end" to all relevant datasets
- Change resource metadata to provide format instead of MIME type
- Update primary key to sqlite syntax
- Use DATETIME instead of DATE type for all dates
- Remove all centroid columns
- Simplified OperationalPresenceView and PopulationView by removing many metadata
fields pulled in from the Dataset, Resource, Org, Sector, Loc, Admin1, and Admin2
tables. These fields weren't required for API queries or API results.