Use TAP to query ESO archive
Currently, ObsPortal uses Astroquery to query the ESO archive. It works well but it seems not very efficient because Astroquery don't use any API and relies on HTML pages parsing...
ESO provides a "Programmatic Access" and we should move to that endpoint using TAP queries. It will allow us to filter headers on the date of last update.
http://archive.eso.org/cms/eso-data/programmatic-access.html