Update unbound.inc

change 'unbound_status' to 'enable' to be consistent with other services and allow detecting enable state from system services
Update unbound.xml

Change 'unbound_status' to 'enable' and advertise the 'dns' system_service. Allows unbound to be discoverable as a dns system service provider so the rest of the system can integrate with it more cleanly.
Add entry for lan interface ipv6 address
Merge pull request #467 from plinss/master

Integrating with pfsense changes in pull request 679