Add selection of options to reservations

Reservations can contain options as described here: https://kea.readthedocs.io/en/kea-2.4.1/arm/dhcp4-srv.html#including-specific-dhcpv4-options-in-reservations so re-use the options specification interface from global here to allow the specification of options in host reservations.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information