Add method for VizieR SED/Photometry viewer

Vizier has a very nice service called sed, where it returns the photometry for a given coordinate. It not exactly clear what catalogues it contain by default, but the goal here as usual, to get the same table the webform returns.

http://vizier.u-strasbg.fr/vizier/sed/

Start by opening the VizieR SED service at http://vizier.u-strasbg.fr/vizier/sed/ and inspect how its web form returns photometry for a coordinate. Compare that response with the existing astroquery VizieR interfaces, then define the method’s expected catalogue and table behavior. Done means the method reproduces the web form’s photometry table.

Written by the indexing model from the issue text.