pvl.hosts.zone: HostZoneError(HostError), move resolve() to pvl.dns.relative(), and expect HostError's in pvl.hosts-forward/pvl.hosts-reverse

# snmp
usr/mibs/

# tempfiles
.*.pyc
.*.sw[op]

# generated files
dist/
MANIFEST
log/
ssl/

# testing
tmp/
test/
var/
opt/