Support non-ICANN DNSLink names

[lidel]

I wrote long elaborate issue about this and then lost it due to github bug, so all you get is this lousy TLDR :(

Configurable DNS resolver is coming (protocol/web3-dev-team#42, multiformats/go-multiaddr-dns#26), we need to fully decouple our stack from ICANN's TLDs:

• remove reliance on TLD safelist from jbenet/go-is-domain as suggested in Transfer to ipfs org? jbenet/go-is-domain#16 (comment) and Add Denarius Domain TLDs jbenet/go-is-domain#19 (review)

• switch DNSLink checks to something equivalent to net.isDomainName (sadly private). The check should only care about the name being compliant with RFC 1035 and 3696, and is not concerned if TLD was blessed by ICANN or some other authority

  • potential candidate: dns.IsDomainName(s string) (labels int, ok bool) from "github.com/miekg/dns"