Draft: Ptlink patches

This merge request contains the changes that are required to render planet debian with PtLink.

As planet debian uses Django-based templates, a translation to a perl-based template language is required, as unfortunately Dotiac::DTL does not work as advertised.

I'll file a companion merge request for the config repository shortly.

I propose that we install this on a separate host name in parallel with the planet venus version of planet debian which can remain on the planet.debian.org hostname for now. This way, the two implementations can be compared and evaluated.

It goes together with config!47