zones/v0 package

EditZone replaces a zone's Info, every field but its slug and status. A curator may edit any pending or approved zone; the proposer may edit their own while it is pending. revision is the zone's Revision the edit was written against: it fails if the zone changed in between, its content or its status. Every edit bumps the revision, so a decision prepared against the old one fails too. A proposer edits only ReviewWindow blocks after the zone was proposed or last edited, and an edit that changes nothing is refused. On a pending zone the reason must be empty; on an approved one it is required and replaces the review on record, so the page names who changed the values, and why. A new chain id sends the zone's verified endpoints back to unverified. Leaving the local kind drops every endpoint on a private host, and is refused while one carries a curator's ruling (a verified one its registrant may withdraw first); the proposer's edit only drops endpoints that are theirs and that they could withdraw on their own (RemoveEndpoint), as for RemoveZone. A new main RPC or gnoweb a stranger (on an approved zone, its proposer too) already lists under its kind would make that listing the zone's own: on a curator's edit it is dropped if nobody ruled on it, and refuses the edit if a curator did; a proposer's edit refuses rather than drop what is not theirs; and a flagged listing refuses the edit whoever holds it. The registry validates the edit before it drops or resets anything, and a refusal reverts the edit with it. A rejected or retired zone cannot be edited.