Fstd2nc

* Fix compatibility issue with older versions of numpy, triggered
when using gridhacks options.

* Fix handling of accented characters from vardicts and metadata
files.
* Removed 'axis' attribute from 2D lat/lon fields, since they are not
truly axes in that case.
* New Python helper function (fstd2nc.extra.get_crs) for getting
projection information from an xarray dataset.
* Turned off annoying librmn messages when using this module from
Python.
* Some support for creating a new Buffer object by instantiating from
an existing Buffer, allowing more specific filtering options.
* Fix filtering for etikets that contain spaces.
* Detect and transform netCDF variable names that contain a '/'.
This can happen, for instance if there are multiple typvars and one
of them contains a '/' character.
* Some support for complex data (datyp=8) from Python interface.
Note: not supported for writing to netCDF, just xarray interface.
* New to_fstd() method to write back to FSTD format instead of netCDF.
* Use only "current" definitions for --opdict and --vardict options,
ignore the obsolete ones.

* Detect newer surface aggregate fields from GEM 5.1 / 5.2 (assign
"sfctype" categories on those fields).
* Detect SWE (from CalDAS) as a surface aggregate field as well.
* New command-line option --sfc-agg-vars to allow the user to specify
additional fields that should be treated as surface-type fields.
* Fix pickling of Buffer objects.
* Fix compatibility issue when using .to_xarray() on Python 3.10.
* Add support for pathlib.Path objects.
* When invoking this module from a Python script, re-route warning and
error messages through the warnings.warn and Exception interfaces
respectively. This will make it easier for the calling script to
filter the warnings and implement exception handling.
* Traduire en (mauvais) français.

* Allow fstd2nc to be "pip install"ed from an environment that doesn't
yet have numpy installed. Installation no longer fails with a weird
error message.
* Fix buggy behaviour when there's a mask field with values > 1.
E.g., values of "2" sometimes represent partially submerged points.
Now treat such points the same as mask value "1" (keep grid point).
* Handle edge case where one of multiple FST input files does not
contain any records.
* Fix --exclude option to properly remove leadtime/reftime again. These
stopped being excludable after some recent code updates in previous
release.
* Fix various bugs in --fstd-compat option.

* New .to_xarray_list() method to return list of variables wrapped in
individual Datasets.
* New command-line --bounds flag, to output grid cell boundaries.
* Remove "leadtime", "reftime", "surface_type", and "station" from
list of coordinates, since some netCDF viewers have trouble with them
being listed in there.
* Fix crash in xarray interface when interpolation is enabled.

* Allow fstd2nc.Buffer objects to be serialized / deserialized.
This allows the objects to be used with the Python multiprocessing
library. Note: not yet compatible with dask multiprocessing, which
seems to use a different mechanism for serialization?
* New keyword args add_px and add_gz for computing pressure or
geopotential height fields in Buffer.to_xarray(). Not available for
command-line usage.
* Allow asymmetric cropping with the --crop-to-smallest-grid option,
i.e., when the smaller grid is not centered inside the larger grid.
* Fixed an address overflow bug when using the xarray interface on
files larger than 4GB.