Add more feature aggregation

[xylar]

This merge adds aggregation for:

• Antarctic regions
• Ocean basins
• Ice shelves
• Transport transects
• MOC basins

[pep8speaks]

Hello @xylar! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2020-11-25 11:32:24 UTC

[xylar]

@milenaveneziani, we had discussed in June (MPAS-Dev/MPAS-Analysis#710 (comment), MPAS-Dev/MPAS-Analysis#712) that it would be really important to have some provenance for the Arctic regions. I had made a draft of what I thought the regions might be but you had mentioned (MPAS-Dev/MPAS-Analysis#710 (comment)) that the regions as you defined them were a little more complicated than this. Could you modify the last commit here to so the aggregator at geometric_features/aggregation/ocean/arctic_regions.py recreates the Arctic regions used in MPAS-Analysis?

[xylar]

This PR still needs to add some documentation on the aggregation functions, how to use them, and how to add new ones.

[xylar]

@milenaveneziani, I'm taking out the Arctic regions for this PR and release. I'll follow up with you about those in the next few weeks.