convert FreeBSD to pkgng with Ansible

Ansible includes a module to manage FreeBSD packages, if you’re using the forthcoming pkgng packaging system. The Ansible module isn’t complete yet, but as Ansible is moving really quickly, I’m pretty confident their FreeBSD support will grow additional knobs. As pkgng is increasingly close to production, and the PC-BSD folks have generously offered their 64-bit pkgng repository available to the public, this seems like a good time to make the move.

But I’m not about to make this change manuall...