pdns convert records view to table

* Rename "records" view to "records_all" (named thusly because it's an aggregate of records_forward and records_reverse and represents the full set of all records)
* Create a "records" table which matches the definition of the view we currently have. This table is missing columns per the documentation, but it is what we are currently using and it isn't breaking anything. I don't want to make any out-of-scope changes for this PR. If we want to match it up with the PDNS docs, we can make another ticket. I did pull the indexes straight out of the docs, though.
* Create a populate_records() function which updates the records table in a single transaction to avoid service disruption. 
* Create a cron job to run the populate_records() function every minute.