Currently DHCPv4 private options are not exposed in D-BUS. This change is to include those private options into D-BUS
Add DHCP vendor specific options to expose in dbus API. This will be added to the JSON output when we query org.freedesktop.network1.Manager object.
Include T1 and T2 DHCPv6 options to expose in dbus API. Introduced new field DHCPv6lease where these options are added. This will be added to the JSON output when we query org.freedesktop.network1.Manager object.