* Add support for SRV records for NAMEDOTCOM and ROUTE53.
* Improve docs
* Rename RR() to ToRR().
* Rename RecordConfig Priority to MxPreference (affects json IR data)
* WIP
* Enable PTR records in dnsconfig.js, in BIND provider.
* Rename REVERSE() to REV().
* More accurate PTR target checking
* Document REV()
* Fix broken test