* DHCP: switch "internal" DHCPv4 plugin from code based on systemd to use nettools'
 n-dhcp4 library.
* Add support for "scope" attribute for IPv4 routes.
* Add support for specifying IAID and FQDN flags for DHCP request.
* Add a '802-1x.optional' property to consider the wired 802.1X authentication as
 optional.
* Use the Network Cost Wi-Fi information element to determine metered
 device state.