DDNS update-optimization

This is one of several tickets to add some of the features for DDNS support from DHCPD to Kea.

In DHCPD there is an option "update-optimization" that allows the administrator to configure if a DDNS update is attempted only when a client seems to have changed or on every renewal.

This feature would allow a Kea server to "heal" the DNS if some of the DNS information had become inconsistent. Specifically it would address the case where an entry has been removed from the DNS without Kea becoming aware of it.