[atlas] Support for arbitrary DNS queries

On Wed, Dec 09, 2015 at 10:49:09AM -0500,
 Shumon Huque <shuque at gmail.com> wrote 
 a message of 26 lines which said:

> I'd like to request the ability to have RIPE Atlas probes be able to issue
> DNS queries for arbitrary record types, and have that capability exposed in
> the API.

By the way, this (real) limit does not seem to be documented in
<https://atlas.ripe.net/docs/measurement-creation-api/> which does not
indicate the possible values for query_type.

> I'm particularly interested in newer DANE reacord types like TLSA,
> OPENPGPKEY, SMIMEA, etc but a general purpose mechanism would be
> useful.

A partial workaround is to use ANY as a query_type.

> Is this feasible? Are others interested in this capability?

Count me in.