MEP -> CNEMC

[lewisblake]

Change Summary

All references to MEP have been changed to CNEMC as this is the new name for the network.

Related issue number

closes #1176

Checklist

• Start with a draft-PR
• The PR title is a good summary of the changes
• PR is set to AeroTools and a tentative milestone
• Documentation reflects the changes where applicable
• Tests for the changes exist where applicable
• Tests pass locally

• With the exception to test_load_berlin as described in this PR

• Tests pass on CI

• with the exception of code coverage which is not relevant for this PR

• At least 1 reviewer is selected
• Make PR ready to review

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.31%. Comparing base (ac80b76) to head (6e100b5).
Report is 511 commits behind head on main-dev.

Additional details and impacted files

@@             Coverage Diff              @@
##           main-dev    #1202      +/-   ##
============================================
- Coverage     79.31%   79.31%   -0.01%     
============================================
  Files           131      131              
  Lines         20230    20231       +1     
============================================
  Hits          16046    16046              
- Misses         4184     4185       +1     

Flag	Coverage Δ
unittests	79.31% <100.00%> (-0.01%)	⬇️

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[thorbjoernl]

Should the following lines in paths.ini also be changed?

L136: MEP = MEP
L176: MEP = 2013

[lewisblake]

@jgriesfeller my vote is to keep the file path in paths.ini the same until the download location on the CAMS Validation Server changes, and then we change the entire name in the AEROCOM_OBSDATA database.