Add access to Data Central Data Aggregation Service

[ddobie]

@sdryder has shown off the Data Central DAS. Ultimately it would be good to implement some of this directly into the pipeline, but in the meantime it is trivial to add a button (similar to the simbad, NED etc buttons) to the top of the page that will automatically bring up the relevant page.

[ddobie]

Should just be a matter of adding the following to here

<a href="https://das.datacentral.org.au/das?RA={{ source.aladin_ra|floatformat:6 }}&DEC={{ source.aladin_dec|floatformat:6 }}&FOV=2.0&ERR=10.0"
class="d-none d-sm-inline-block btn btn-sm btn-info btn-icon-split shadow-sm" target="_blank"
title="Data Central cone search with a 10 arcsec radius.">
<span class="icon text-white-600">
  <i class="fas fa-info-circle fa-sm"></i>
</span>
<span class="text">DAS</span>
</a>