PublicDNS: move static data to YAML.

Also, slightly reorganize how it is stored to make it more friendly for
human editing.
DuckDuckGo: move static editable data to YAML.

This seems like it should make maintenance easier.
dist.ini: Add YAML to Prereqs.

Even though it is implicitly required (at present) for duckpan, being
explicit makes it clear that we are actually using it in local code.
Still, we'd rather not make it depend on a particular version, so as
not to conflict (or bloat.)  YAML is pretty stable, so this should
be fine.

Also remove a no-longer-required `use YAML` from the ZappBrannigan
Goodie.
Merge pull request #428 from mwmiller/yaml_data

YAML for Static Data.