Added section 'Adaptive Masking' to Masking.ipynb

[sol1105]

This PR

• adds a section to the documentation (in Masking.ipynb) explaining the adaptive masking technique (skipna and na_thres parameters of Regridder.__call__).
• corrects a typo in the explanation of skipna in frontend.py.

In the regrid_nomask example in Masking.ipynb I changed the weights creation from "conservative_normed" to "conservative" so I can use this weights in the adaptive masking example. This should not affect the regrid_nomask example.

I'm happy for feedback regarding the wording :)

[review-notebook-app[bot]]

Check out this pull request on 

See visual diffs & provide feedback on Jupyter Notebooks.

---

Powered by ReviewNB