The domain name flag should be reworked if it is used for more than just DNS

[jbarnes]

If I have no desire to setup a Route53 DNS entry, cfn-seed enforcing a "domain name" requirement because it uses it for other naming purposes should be reworked.

cloudformation-seed: error: the following arguments are required: -d/--dns-domain

I'd recommend a new naming convention flag be added to cfn seed, the dns-domain flag then uses this partially or fully if set, but I don't feel enforcing a dns-domain when it's not actually necessary makes sense, if it's for naming purposes then explicitly definie it as for naming purposes.