PR collecting changes in the plot module

[mberz]

Which issue(s) are closed by this pull request?

Closes #215, #211, #183, #223

Changes proposed in this pull request:

• Allow passing list of two axes (2nd for colorbar) and return colorbar for balloon like plots Plots/Refactor balloon plot (ax, colorbar) #220
• ... balloon_wireframe + colorbar encoding bugfix Plots/Refactor balloon_wireframe plot (ax, colorbar) #224
• ... contour Plots/Refactor contour plot (ax, colorbar) #225
• ... contour_map Plots/Refactor contour_map plot (ax, colorbar) #227
• ... pcolor_map Plots/Refactor pcolor_map plot (ax, colorbar) #230
• ... pcolor_sphere Plots/Refactor pcolor_sphere plot (ax, colorbar) #233

Todo

• remove if function.__name__ in cases from tests: once all plot functions have been refactored, the tests can be fully adapted to the new behavior. Until then, we need to differentiate between functions with new ax input / return and ones that haven't been refactored yet. Plots/remove if function.__name__ in [...] from test_plots.py #237
• Add None as return for cb (contour_map, balloon) Plots/harmonize return parameter documentation #231
• Add list[matplotlib.axes.Axes]as return for ax (contour_map, balloon) Plots/harmonize return parameter documentation #231
• Adjust ref to matplotlib projections for contour_map Plots/contour_map link to maptlotlib-projections #232
• create baseline plots once all changes are collected Plots/Create baseline plots #242
• Fix obstructive colorbar placement / Add style parameter Plots/Add style parameter to plot module #257
• change examples to nicer plots (x / y) Docs/Adjust example plots for balloon and balloon_wireframe #262
• Add short description on how to customize plots using mpl top level to plot docs Plots/Add general guide on the overlap issue #263

Note

• In comparison to the current baseline figures for balloon plots the default for the colormap encoding has changed from old parametrization phase=False to cmap_encoding='phase'

[mberz]

Thanks @hoyer-a, I did a quick review of the changes but cannot submit it since I've opened the original PR.
Since all changes have been reviewed individually I'd suggest to not do in-depth reviews anymore at this point.
If that's alright, I'll merge the PR later today.