Compatibility fixes for scipy and matplotlib

Compatibility fixes, cli improvements and code formatting

Minor fix for grid files

Minor fix for grid files (#53)

plugin entrypoint compatibility fix for python 3.7 (#50)

Fix for compatibility with python 3.7 (#50)

Changed
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* plugin entrypoint compatibility fix for python 3.7 (#47)
* ignore SNF links in linkcheck (#49)
* Replace gitter (#45)

Compatibility fixes for matplotlib 3.5 and python 3.10

Compatibility fixes and minor improvements, see #46 for full details.

Added
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-   An abstract `convert_coordinate` method has been implemented for the  `Plotter` and `Formatoption` class that can be used in subclasses to convert coordinates for the required visualization. The default implementation does nothing (see #39)

Fixed
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-   the update method now only takes the coordinates that are dimensions in the dataset, see #39
-   psyplot is now compatible with matplotlib 3.5 and python 3.10

Changed
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-   loading more than one variables into a `DataArray` now first selects the corresponding dimensions, then puts it into a single `DataArray`. This avoids loading the entire data (see #39)

Compatibility fixes and LGPL license

Fixed
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-   psyplot is now compatible with xarray 0.18

Added
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-   psyplot does now have a CITATION.cff file, see https://citation-file-format.github.io

Changed
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-   psyplot is now officially licensed under LGPL-3.0-only, see [\#33](#33)
-   the lower bound for supported xarray versions is now 0.17.
-   project files do not store the Store anymore as this information cannot be gathered from xarray 0.18. We now rely on xarray to automatically find the engine to open the files.
-   Documentation is now hosted with Github Pages at https://psyplot.github.io/psyplot. Redirects from the old documentation at https://psyplot.readthedocs.io have been configured.
-   Examples have been removed from the psyplot repository as they now live in a central place at https://github.com/psyplot/examples
-   We use CicleCI now for a standardized CI/CD pipeline to build and test the code and docs all at one place, see [#32](#32)

Patch for a better support of 3D bounds

New repository, presets and compatibility fixes

Support for xarray=0.12, cdo=1.5 and docrep=0.2.6

Better unstructured grid support and ready for python 3.7