Rename/remove a few policy params and archive some pre-TCJA reforms

[martinholmer]

This pull request resolves issue #2215.

Requesting review by @MattHJensen @codykallen @hdoupe @andersonfrailey @Peter-Metz

[codykallen]

@martinholmer, these changes look good to me.

@andersonfrailey, it looks like there's some potential for merge conflicts between your PR #2222 and @martinholmer's PR #2223.

[martinholmer]

Reforms test fails on GitHub but passes on my computer. Will investigate this afternoon.

[codecov]

Codecov Report

Merging #2223 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #2223   +/-   ##
======================================
  Coverage     100%    100%           
======================================
  Files          12      12           
  Lines        2976    2981    +5     
======================================
+ Hits         2976    2981    +5

Impacted Files	Coverage Δ
taxcalc/policy.py	100% <100%> (ø)	⬆️

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