[atlas] Proposal: Remove support for non-public measurements [ONLY-PUBLIC]

Hi,

> The definition of a "small" test could be something like;
> - maximum 20 probes
> - runs for maximum 60 minutes
> - is repeated maximum 10 times
>    (if you run every 300sec you have to limit the endtime to 50 minutes)

What would you propose the API to do if this rule is violated? Should it 
outright refuse the measurement, or should it silently turn on the 
public flag (silently, because even if we emit a warning, it is probably 
never seen by a human...)?

> With such limits you can troubleshoot things (non-publicly) but you 
> can't build your monitoring system on top of that.

I guess this hinges on what level of support (legal, technical or other) 
we're aiming for when it comes to others building services on top of 
RIPE Atlas.

Regards,
Robert