* add GeoIP policy
* handle empty lists of ASNs and countries
* handle missing GeoIP database or missing IP from the database
The exceptions raised here are `PolicyException`s to let admins bypass
an execution failure.
* fix translations
whoops
* remove `GeoIPPolicyMode`
Use the policy binding's `negate` option instead
* fix `DataProvision` typing
`ak-dual-select-provider` can handle unpaginated data
* use `django-countries` instead of a static list of countries for ISO-3166
* simplify `GeoIPPolicyForm`
* pass `GeoIPPolicy` on empty policy
* add backend tests to `GeoIPPolicy`
* revise translations
* move `iso-3166/` to `policies/geoip_iso3166/`
* add client-side caching to ISO3166 API call
* fix `GeoIPPolicy` creation
The automatically generated APIs can't seem to handle `CountryField`,
so I'll have to do this by hand too.
* add docs for GeoIP Policy
* docs: stylize
add review suggestions from @tanberry
* refactor `GeoIPPolicy` API
It is now as declarative as I could make it.
* clean up `api.py` and `views.py`
