Remove code related to Postgres zone storage.

Start documenting JSON zone loading.
Add a put_zone/2
Add support for deleting zones.
Debug the response to encode.
Handle various dns:encode_message responses.
send_tcp_message takes 2 args.
Replace old sys.config.
Do not time building the named index.
Use R16.
Switch several info logs over to debug.
Switch from info to debug.
Add support for loading zones remotely and from a zone server.
Ignore local zones.json
Removed dependency.
Allow custom zone record parsers to be registered.
Update sample zone.
Merge branch 'feature/json-zone-loading'