Version 0.5.0

• Add read and write functionality for interchange format
• Add csv reading capabilities in pm2io module for wide and long (tidy) CSV files.
• Add da.pr.coverage() and ds.pr.coverage() functions to summarize data
  coverage.
• Add aggregation functions set and count which use aliasing and can reduce to
  a given set of dimensions, including the entity.
• Update python packaging to use declarative style and modern setuptools.
• Support and test python 3.9 and windows.
• Add dataset attr for storing the terminology used for entities (and thus variable
  names).

Version 0.4.0

• Add the da.pr.set() and ds.pr.set() functions for overwriting / infilling /
  extending data.
• Allow for more than one source in a single Dataset / DataArray.
• Support xarray 0.17, and therefore drop support for Python 3.6.

Version 0.3.1

• Re-release 0.3.0 to trigger zenodo.

Version 0.3.0

• Add functions for downscaling and aggregation of gas baskets and categorical baskets.
• Add functions, docs, and tests for basic GWP handling.
• Add Makefile target to generate patched stub files for xarray containing the primap2
  API.
• Add development documentation detailing the structure of the repository and the tools
  used to development of PRIMAP2.
• Add selection and indexing which understands dimension names like area in addition
  to the full dimension key including the category set like area (ISO3). Works with
  ds.pr[key] and ds.pr.loc[selection] as well as da.pr.loc[selection].
• Add usage documentation for all currently included functionality.
• Access metadata easily via properties like ds.pr.references.