Revise tc.py to produce CSV-formatted output files

[martinholmer]

This pull request is the latest in a series of pull requests that redesign the command-line interface (CLI) to the taxcalc package so that its primary focus is tax analysis rather than validation. The earlier pull requests in this series are #1225 and #1228. There will be at least one more in the series because the --graph option is not yet active.

@MattHJensen @feenberg @Amy-Xu @andersonfrailey @GoFroggyRun @codykallen @zrisher

[codecov-io]

Codecov Report

Merging #1232 into master will decrease coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #1232      +/-   ##
=========================================
- Coverage   99.22%   99.2%   -0.03%     
=========================================
  Files          38      38              
  Lines        2719    2650      -69     
=========================================
- Hits         2698    2629      -69     
  Misses         21      21

Impacted Files	Coverage Δ
taxcalc/taxcalcio.py	99.37% <100%> (-0.19%)	❌

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