Add DNS-PERSIST-01 challenge support

- Add dns-persist-01 to allowed challenge types in verify_config()
- Implement dns-persist-01 case in challenge preparation (no dynamic token)
- Skip deployment and cleanup for dns-persist-01
- Update help text and documentation
- Add man page and README updates
- Update CHANGELOG

docs/man/dehydrated.1

@@ -26,7 +26,7 @@ single certificate valid for both "example.net" and "example.com" through the \f
 Alternative Name\fR (SAN) field.
 
 For the next step, one way of verifying domain name ownership needs to be
-configured.  Dehydrated implements \fIhttp-01\fR and \fIdns-01\fR verification.
+configured.  Dehydrated implements \fIhttp-01\fR, \fIdns-01\fR, and \fIdns-persist-01\fR verification.
 
 The \fIhttp-01\fR verification provides proof of ownership by providing a
 challenge token. In order to do that, the directory referenced in the
@@ -44,6 +44,12 @@ the software or the DNS provider at hand, there are many third party hooks
 available for dehydrated.  See \fIdns-verification.md\fR for hooks for popular
 DNS servers and DNS hosters.
 
+The \fIdns-persist-01\fR verification works by providing a persistent DNS record
+containing account information. Unlike \fIdns-01\fR, this requires setting up a
+static TXT record once that remains in place indefinitely. No dynamic DNS
+updates are performed during certificate requests. See \fIdns-verification.md\fR
+for details on setting up the required DNS record.
+
 Finally, the certificates need to be requested and updated on a regular basis.
 This can happen through a cron job or a timer. Initially, you may enforce this
 by invoking \fIdehydrated -c\fR manually.