Add Zonal and Meridional Mean calculation from recipes.py

[CPKalb]

Describe the New Feature

Add in the calculations to perform the zonal and meridional means into METcalcpy. The code to do this is located here:https://github.com/zdlawrence/pyzome/blob/master/pyzome/recipes.py. Likely we will want to make the code more general, so that they can take a variety of different variable names, if this is possible

Acceptance Testing

I've been testing with the ERA on glade, but this was also suggested: https://www.ncei.noaa.gov/data/sudden-stratospheric-warming-compendium/access/

Time Estimate

Estimate the amount of work required here.
Issues should represent approximately 1 to 3 days of work.

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Relevant Deadlines

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Funding Source

2773542

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Define Related Issue(s)

Consider the impact to the other METplus components.

• METplus, MET, METdatadb, METviewer, METexpress, METcalcpy, METplotpy

New Feature Checklist

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