Address schema

Addresses are geographic points used for locating businesses and individuals. The rules, fields, and fieldnames of an address can vary extensively between locations. We use a simplified schema to capture worldwide address points. This initial schema is largely based on the OpenAddresses (www.openaddresses.io) project. The address schema allows up to 5 "admin levels". Rather than have field names that apply across all countries, we provide an array called "address_levels" containing the necessary administrative levels for an address.