When doing rollover in a timely manner we need to have access to the
relevant kasp configured durations.
Most of these are simple get functions, but 'dns_kasp_signdelay'
will calculate the maximum time that is needed with this policy to
resign the complete zone (taking into account the refresh interval
and signature validity).
Introduce parent-propagation-delay, parent-registration-delay,
parent-ds-ttl, zone-max-ttl, zone-propagation-delay.
Write functions to access various elements of the kasp structure,
and the kasp keys. This in preparation of code in dnssec-keygen,
dnssec-settime, named...
This stores the dnssec-policy configuration and adds methods to
create, destroy, and attach/detach, as well as find a policy with
the same name in a list.
Also, add structures and functions for creating and destroying
kasp keys.
