Move all catalogs connected with a single survey underneath the directory structure

[nevencaplar]

At the moment various associated, margin, index catalogs are made as independent catalogs and we have to ``artificially'' connect them. Make such catalogs integral part of each survey catalog, so that they are avaliable immedietly.

This ticket to be followed by tickets to generate margin and index catalogs automatically when importing.

[delucchi-cmu]

I'd suggest keeping the single directory structure for a single catalog and type, but enforcing more of the convention we've been using, and creating some API sugar around it. e.g.

    * gaia_dr3/
        * hats.properties
        * catalog/
            * properties
            * ...
        * margin_5arcs/
            * properties
            * ...
        * index_designation/
            * properties
            * ...
        * spectra/
            * ...

and the hats.properties file can contain more information about the relationships between catalogs, similar to what the almanac is (poorly) providing.