rename and move data maniplation functions

[mathause]

edited the title after #274. The old title was rename the xarray_utils?

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It's a bit a generic, bland name and does not say much. Also @jschwaab prefered something else. Worth reconsidering before v0.9.0

[mathause]

See #217 for ideas

[mathause]

My current idea is to make them "first level citizens" (not sure if this is the correct term), i.e.:

mesmer.grid
mesmer.mask
mesmer.weighted

mesmer.grid.wrap_to_180(...)
mesmer.mask.mask_ocean(...)
mesmer.weighted.global_mean(...)

where I would move the .py files to core and then import from there. I don't like to have them two levels down (mesmer.process.grid.stack(...)) and I don't know what a good name for the first level should be anyway.

[mathause]

Happy to reconsider if there is a better idea...

[mathause]

After #274 I renamed this issue as I am not yet sure that the names are final (i.e. if I am totally happy with them). This concerns:

mesmer.mask.mask_ocean_fraction
mesmer.mask.mask_ocean
mesmer.mask.mask_antarctica

mesmer.globmean.lat_weights
mesmer.globmean.weighted_mean

mesmer.core.computation.calc_geodist_exact
mesmer.core.computation.gaspari_cohn

• calc_geodist_exact, gaspari_cohn, and lat_weights could go to mesmer.geo or mesmer.geog.
• mesmer.globmean.weighted_mean could be renamed to mesmer.weighted.global_mean. Or this could even go to mesmer.stats.weighted?
• mesmer.mask could go to mesmer.region, or also to mesmer.region (I am not super happy having mask twice in a row (i.e. mesmer.mask.mask_ocean_fraction), but they could just as well stay...

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I am happy with mesmer.grid:

mesmer.grid.wrap_to_180(...)
mesmer.grid.wrap_to_360(...)
mesmer.grid.stack_lat_lon(...)
mesmer.grid.unstack_lat_lon_and_align(...)
mesmer.grid.unstack_lat_lon(...)
mesmer.grid.align_to_coords(...)

[mathause]

• mesmer.globmean certainly needs renaming
  • Move this to mesmer.weighted
  • Add a new function global_mean(da, weights=None, x_dim="lon", y_dim="lat") which calculates the lat weights if not given.
• I recently thought of geospatial - so calc_geodist_exact could go to mesmer.geospatial.calc_geodist_exact
• Need to think if I move e.g. "mesmer/core/grid.py" to "mesmer/grid.py". Organisation-wise I don't like it but sphinx-autosummary does not work well otherwise...

[mathause]

closing in favor of #348