Support DNSCrypt https://dnscrypt.org

```
It would be pretty neat to have Namebench support DNSCrypt.

This requires retrieving the current list of public DNSCrypt servers, spawning 
a proxy for each of them, and giving the ability for Namebench to test only the 
DNSCrypt servers.

```

Original issue reported on code.google.com by `chrysa...@gmail.com` on 4 Aug 2015 at 10:30
