Review and redesign of ColocatedData

[jgliss]

Similar to #146, also ColocatedData should undergo some redefinition (but not as much as StationData. Suggestion is to turn ColocatedData.data attr. from a xarray.DataArray into a xarray.Dataset with individual DataArrays being assigned to it for model and obs separately (this would get rid of data_source dimension).

Right now I think it should still be single variable (encoded in filename).

Names of the "variables" of the Dataset could then be the obs / model IDs and would allow easy access of the individual subsets and would also make it easier to add other model or observation records. And it would also allow easier separation of global metadata (set in Dataset, e.g. pyaerocom colocation settings) and model / obs metadata (set in individual DataArray instances for both "variables").

[github-actions[bot]]

This issue is stale because it has been open for 365 days with no activity. This issue will be closed in 14 days if no action is taken.

[lewisblake]

Ideally these would be make CF compliant so that standard tools can easily work on them.