public.json: Use local definitions for address and geo

Swagger doesn't support extenal $ref's yet [1], so don't link out to
json-schema.org.  I made some changes to the definitions as I brought
them in:

* I dropped the 'dependencies' section from the address schema,
  because Swagger doesn't support it [1].
* I added float formats to the geo properties [2], since we don't need
  double precision.
* I made both latitude and longitude required for geo, since the whole
  drop.geo entry is optional, and it's not very useful to set only one
  of lat/lon.

[1]: https://github.com/swagger-api/swagger-ui/issues/721#issuecomment-62943482
[2]: https://github.com/swagger-api/swagger-spec/blob/master/versions/2.0.md#data-types