Some documentation incomplete

[lrbusquets]

The page documenting the observatins module in the API (https://py.api.tudat.space/en/latest/observation.html#) has 8 "TODO"s distributed througout the method descriptions. Although it is expected if the documentation is somewhat in progress, this made things a bit confusing when I was adding viability settings in my simulations.

[larshinueber]

Hi @lrbusquets, it seems this has been resolved in the meantime? Feel free to add any specific functionality you're missing to #211, where undocumented functionality is now tracked :)