Only sync Route53 Domains

[Chris Dawes]

We have some customers using cloudflare and some using route53.

It would be great if we could sync only the domains using route53 and not auto-create domains as we are charged for every domain on route53 regardless of it it is being used or hosted elsewhere.

This plugin is only useful if you have all of your domains at Route53, which is pretty rare.

So this extension should:

1. Have a global list of domains activated for route 53
2. Allow domains to be synced from the domain level to route53
3. Have a toggle on/off to indicate if new domains should be automatically put on route53 (restoring current functionality)