[PowerDNS] Backends in detail: PipeBackend

Thought of submitting this when another PowerDNS submit came up.

The pipe backend is a very interesting one since it allows you to hack up a custom DNS resolution mechanism very easily. For instance I built a simple backend that synthesizes DNS records from LDAP items for much easier domain management.

To mod: please do not remove the "pipebackend" from the title since it is the reason I'm sharing this... Perhaps I should have written it as [PipeBackend].