Ellaborate "Client Blocklist" to use the EDNS Mac-address option (65001)

[cbuijs]

For client-blocklist it would be nice to also be able to filter baed on on mac-address.

Either straight from the query (hard to do and not uniform on different platforms), or just from EDNS Option 65001.

We discussed this earlier in #105 already, but I think supporting macs in a list utilising EDNS Option 65001 is quite accepted standard nowadays (see PowerDNS, DNSDist and DNSMasq for example).

[folbricht]

This was more complex that I thought but there's an implementation on issue-398 branch. Can you give it a try? I added a unit test but haven't been able to test fully end-to-end.