Cleanup work for the pdns cookbook

This PR encompasses an effort to modernize and upgrade the current state of the pdns cookbook. Since before adopting this cookbook, we've been working on adding additional PowerDNS installations in production at DNSimple. Our overall goal will be to make this a fully tested and reusable library cookbook for everyone to use with sane defaults from an experienced DNS provider.

Two big items in the pull request encompass separating the concepts of running a resolver and an authoritative name server. You can do both at once if you see fit and in fact they are treated as separate programs under the same grouping of PowerDNS. We've re-named the 'server' portions to 'authoritative' for lack of a better name.

We've also begun converting all the broken BATS tests to ServerSpec and will be filling in the gaps with live queries to test the servers in various configurations.