date based serial numbers

complicated by OGMG-it's-2014-and-we're-still-using-unsigned-32-bit-ints
add mkSOA
add dns records to Attr
my secondary dns server now uses Ip Attrs
better serial number offsets
genZone is working! complete DNS zone file generation from propellor config
Dns.primary wrote, not quite ready
fix
rename TTL field, per RFC 2308
provide a way to specify real cnames
add SOA
The `cname` property was renamed to `aka` as it does not always generate CNAME in the DNS.
Propellor can configure primary DNS servers, including generating zone files, which is done by looking at the properties of hosts in a domain.
rename aka to alias
make primary dns server beat secondary if both are defined for a domain

Made my config file simpler..
secondaryFor
propellor spin