pyicon/pyicon_tb.py: Fixed bug in level interpolation (calc_vertical_interp_weights and zonal_average_atmosphere). New function nctime_to_datetime64 to calculate numpy.datetime64 objects from netcdf time.

notebooks/examp_plot_timeseries.ipynb: Added new notebook to demonstrate how time series can be plotted.

pyicon/pyicon_tb.py: Changed radius_of_influence and convert np.nan in apply_ckdtree to masked values everytime (this was prob a bug before).

conda_act_mistral_pyicon_env.sh: Need to go back to myenv_py3 since pyicon_py38 seems not to work anymore with ipython.

example_scripts/examp_pyicon_bstr_polar.py: Example to plot barotropic streamfunction in the Arctic.

New config_ckdtree/config_ckdtree_np.py: to calculate ckdtree inds and dists for North Pole optimised projections.

view/pyicon_view.py: More flexible way of using pyic.plot_settings. Try to start with 0.3 deg grid at start up instead of old default 0.1 which took always a long time to load.

switching to new python env.

  * a bit of rearanging routines to get a more logical order
  * new intermediate function: ckdtree_points to calculate grid points
  * new function: calc_north_pole_interp_grid_points for a more
    appropriate grid for polar projections
  * new functions: spherical_to_cartesian and cartesian_to_spherical
  * splitting: mask_big_triangles

pyicon_plotting.py and pyicon_quickplots.py: Allowing contour lines being overlaid of plots by using argument conts in plotting functions.

Notebooks: Renaming notebooks/test_arrange_axes.ipynb -> notebooks/examp_arrange_axes.ipynb. Listing all three %matplotlib XXX options in first cell.

quickplots/qp_driver.py: Added matplotlib.use('Agg') to make batch jobs possible. Added new figures: fig_names += ['atm_temp_zave', 'atm_u_zave', 'atm_v_zave', 'atm_rel_hum_zave'] and fig_names += ['atm_cloud_cover_zave', 'atm_cloud_water_zave', 'atm_cloud_ice_zave', 'atm_cloud_water_ice_zave']

pyicon_plotting.py: new vertaxtype variable to decide whether to use ocean or atmosphere vertical axes. New implementation of minor xticks.