Fix mode for AggregateNetworkObjects

[greenape]

Closes #651

I have:

• Formatted any Python files with black
• Brought the branch up to date with master
• Added any relevant Github labels
• Added tests for any new additions
• Added or updated any relevant documentation
• Added an Architectural Decision Record (ADR), if appropriate
• Added an MPLv2 License Header if appropriate
• Updated the Changelog

Description

Fixes calculating a modal average with aggregate network objects by applying the required special case, and changes the column name to value rather than having it vary with the stat you asked for.

[codecov]

Codecov Report

Merging #663 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #663      +/-   ##
==========================================
+ Coverage   93.49%   93.49%   +<.01%     
==========================================
  Files         125      125              
  Lines        6271     6274       +3     
  Branches      665      666       +1     
==========================================
+ Hits         5863     5866       +3     
  Misses        284      284              
  Partials      124      124

Impacted Files	Coverage Δ
...wmachine/features/network/total_network_objects.py	97.22% <100%> (+0.12%)	⬆️

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