[atlas] Replacing "ping RRDs" with "zoomable ping graphs"

Dear RIPE Atlas users,

As you may have read in the recent RIPE Labs article
(https://labs.ripe.net/Members/becha/seismograph-and-other-new-ripe-atlas-features),
we've replaced the old style, RRD based visualisation for built-in ping
measurements with client side, zoomable graphs. Since then we've also
changed the graphs that represent the probe's bandwidth usage.

The new graphs have the benefit that they retain all details, even for
longer time intervals. (These details were lost in the RRD based graphs over
time.) Other reasons why we changed include that generating the RRD graphs
did not scale well with the increasing number of RIPE Atlas probes, and
making them required us to maintain a large set of backend servers, each
being a single point of failure.

With the new approach you still have visualisations for this information,
with more details and interactivity (though it does require running
JavaScript on the client side).

We'll change the remaining RRDs to this new model as well in the coming
period, and stop generating the RRD based images altogether. We expect to
stop with the "built-in pings" and the probe traffic RRDs first, likely in
the second week of October.

If you would like to embed these new style visualisations into your pages
(maybe because you used the RRD graphs before), then you'll have to embed a
RIPEstat widget; see
https://stat.ripe.net/widgets/demo/atlas_probe_widgets.html for details.

Regards,
Robert Kisteleki
for the RIPE Atlas team