Add NCHS mortality geo aggregation at the HHS and nation levels#1243

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alexcoda wants to merge 5 commits intocmu-delphi:mainfrom

alexcoda:nchs_geo_aggregation

Commits on Aug 20, 2021

NCHS data available at HHS, nation level
zhuoran-Cheng16
committed

Commits on Sep 11, 2021

Merge branch 'main' into nchs_geo_res
alexcoda
committed

Commits on Sep 14, 2021

Commits on Sep 17, 2021

Pull out repeated functionality into helper methods
alexcoda
committed