Document the list of HiPS identifiers that can be set to aladin.survey

[tboch]

[tboch]

We could have a method

aladin.find_hips(keywords='my keywords', in_view_only=True|False)

[ManonMarchand]

note to implement: we can call astroquery.mocserver
see https://astroquery.readthedocs.io/en/latest/mocserver/mocserver.html#query-for-hierarchical-progressive-surveys-hips (only in astroquery >=0.4.9)