Metview

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- new argument to setoutput(plot_widget=) - default True, set False to allow images to be saved into the notebook
- multi-page plots in Jupyter notebooks now contain the animation controls by default

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- added automatic play and speed controls to animated plots in Jupyter notebooks

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- added animate=True argument to plot() command for animated plots in Jupyter notebooks
- allowed cfgrib backend keyword arguments to be passed to Fieldset.to_dataset()
- Fieldset out-of-range indexing now raises an IndexError
- Fieldset merge() function now allows a single Fieldset as argument

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- renamed function download_gallery_data() to metview.gallery.load_dataset()

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- added new function download_gallery_data() to download Gallery example data files
- added write(filename) method for classes Fieldset, Geopoints, GeopointSet, Bufr and NetCDF
- added ability to construct a Fieldset from a list of Fieldsets: Fieldset([f1, f2, f3])
- added metzoom function (for the future)
- added keyword arguments to setoutput('jupyter') to control output size in notebooks
- added metview_python member to result of version_info() function

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- temporarily removed tests that involve writing xarrays as GRIB