dynamicdns: Implement a Dynamic DNS service on foundation servers

• Modify GnuDip or find a new server with following properties
• Has support for IPv6
• Has support for CAPTCHA when registering account
• Verifies email address (using a verification link) before creating an account.
• Give full NS control of the subdomain.
• Support both IPv4 and IPv6 at the same time.
• Allow registration through API.