Strip catalog attributes - Optional reconstruction version.

[aulemahal]

Pull Request Checklist:

• This PR addresses an already opened issue (for bug fixes / features)
  • This PR fixes save_to_* should remove catalog-dependent attributes. #499 and fixes Official path scheme for reconstruction shouldn't require a version. #500.
• (If applicable) Documentation has been added / updated (for bug fixes / features).
• (If applicable) Tests have been added.
• This PR does not seem to break the templates.
• CHANGELOG.rst has been updated (with summary of main changes).
  • Link to issue (:issue:number) and pull request (:pull:number) has been added.

What kind of change does this PR introduce?

• New strip_cat_attrs utility to remove those attributes added by the catalog opening functions.
  • Use this by default in save_to_zarr and save_to_netcdf.
• In build_path, added possibility to have aggregated folder levels with optional components.
  • Make version optionnal in the non-sim schemas.

Does this PR introduce a breaking change?

• Yes. Saved files will have a few attributes removed.
• Yes. build_path will not fail on a reconstruction dataset missing a version.