CHANGES

1. Most tasks touched to use netCDF4 inferencedata file.
2. Added netCDF4 metadata copy to covid.util
3. Updated model_spec.py to use xarray
4. Updated covid.ruffus_pipeline to use netCDF4 files, adding pipeline metadata
5. Updated pyproject.toml
6. Removed chunk specification in inference.py.  Defer to automatic chunking for now.

CHANGES:

1. Committed missing `case_data.py` file
2. Moved pipeline specification into `covid.ruffus_pipeline`
3. Moved pipeline initialisation into `covid.pipeline`