Add Ondrej's dns proposal in its original form
219-expanded-dns: Isolate the references to DNSSEC

This was originally a DNSSEC proposal, but the round trip issue makes
it look as though this proposal is not sufficient to implement DNSSEC
for practical use.
219-expanded-dns: Clarify the exact packet format.

Also, make it a bit more extensible, in case we do get multi-packet
responses working in the future.
219-expanded-dns: finish my edits

These are mainly about how to normalize requests and responses, plus a
few security notes.
219-expanded-dns: include some XXs from Ondrej
Tweak 219 a little more
Add an Ed25519 identities proposal and a kill-create_fast proposal