move workaround logic to utilities module
set CNAME migration to clobber conflicts
CNAMEs unique by label and domain
better notification for broken foreign keys
migrations don't crash on cname validation errors
create more reverse SOAs at migration
don't create in-addr.arpa and add views to all nameservers
Properly handle blank MAC addresses

Blank MAC addresses were permitted regardless of the value of
dhcp_enabled. Now they're only permitted if dhcp_enabled is false.
Specify MAC address so object validates
Specify email so Git doesn't freak out
Don't validate MAC until MacAddrField.clean
Remove cruft
Make 00:00:00:00:00:00 an invalid MAC address
Re-add hint to disable DHCP
actually migrate reverse zones
Merge pull request #636 from drkitty/fix-tests-again

Specify email so Git doesn't freak out
Merge pull request #627 from murrown/label_domain_workaround

CNAME migration fix
Allow empty MAC addresses when DHCP is disabled

Also fix an error message bug
Force Django to always clean the 'mac' field
Make 'always_validate' attribute optional

(It was always supposed to be optional, but I messed up the first time.)