Add DNSSEC

[ianbogda]

This PR is proposal to add secure on the DNS

• DNSSEC
• prevent hack from rainbow tables

Ability to have more than 1 DNS (should be 2 or 3+)

[dstapp]

Hey, sorry for the late response. Looks good, thanks! I will review it in detail and then merge it.

[dstapp]

@ianbogda When I create a image from your fork, run "make server_test" to start the container and then "make api_test", the following request fails:

curl "http://localhost:8080/update?secret=changeme&domain=foo&addr=1.2.3.4"
{"Success":false,"Message":"exit status 2: update failed: SERVFAIL\n","Domain":"foo","Address":"1.2.3.4","AddrType":"A"}

Any insights on this?

[adolgoff]

Hey, first, @dprandzioch thanks for the project, and @ianbogda - thanks for updates!
@ianbogda could we maybe create persistence commit as a separate PR? Seems to be very easy fix, and for sure very important one. If you want I could do this MR from my side.