Improve differentiation between Embedded and NE Codelists

[hayfield]

Codelists are managed in multiple different manners, leading to the categorisations Embedded and Non-Embedded. It is not currently possible to differentiate between Codelists that are manged in different manners in a clear and obvious manner.

It should be possible throughout pyIATI to obtain and differentiate between types of Codelists as appropriate.

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• Add an attribute to the Codelist class to detail the management status (as noted in Implement missing attributes on Codelists #166)
• Resources
  • Determine whether the codelists_non_embedded/ resource folder should be renamed to version_independent/codelists/ (and if so, change it!)
  • Make iati.resources.get_codelist_paths(iati.version.STANDARD_VERSION_ANY) return a list of Non-Embedded Codelist paths
  • Add way to get just Embedded Codelist paths (either a flag to get_codelist_paths(), or a distinct function)
• Default
  • Make iati.default.codelists(iati.version.STANDARD_VERSION_ANY) return only Non-Embedded Codelists
  • Add way to get just Embedded Codelists (either a flag to codelists(), or a distinct function)
• Embedded / Non-Embedded / Replicated
  • Determine whether any changes are required to distinguish between 3 different management strategies (Minor / Major / All)