Add --sqldb option to tc CLI

[martinholmer]

This pull request adds a new output option that writes the dump output to the dump table in a SQLite3 database. The reason for adding this option is to reduce the size of dumped output file and to provide an easier way to tabulate the dumped output. The --dump option still generates a CSV-formatted file containing the dumped output, which keeps open the possibility of users importing the dumped output into a wide variety of data-analysis software packages (ranging from SAS or R or Stata to any spreadsheet).

Here is an example that uses the new option:

$ tc puf.csv 2020 --dump --sqldb
You loaded data for 2009.
Tax-Calculator startup automatically extrapolated your data to 2020.

$ ls -l puf-20*
-rw-r--r--  1 mrh  staff  200983336 Apr 24 11:10 puf-20-#-#.csv
-rw-r--r--  1 mrh  staff  115200000 Apr 24 11:11 puf-20-#-#.db

$ cat tab.sql
select count(*),
       sum(s006)*1e-6,
       sum(iitax*s006)*1e-9,
       sum(payrolltax*s006)*1e-9
from dump;

$ sqlite3 puf-20-#-#.db <tab.sql
219814|177.802211679916|1876.83747004077|1224.89833083698

$ csvvars puf-20-#-#.csv | grep s006
140 s006
$ csvvars puf-20-#-#.csv | grep tax
51 iitax
. . .
154 payrolltax

$ awk -F, 'NR>1{n++; w=$140; sw+=w; sit+=w*$51; spt+=w*$154}
           END{print n, sw, sit, spt, mtr}' puf-20-#-#.csv
219814 1.77802e+08 1.87684e+12 1.2249e+12

Notice that the SQLite database file is only slightly more than half the size of the CSV-formatted file containing the exact same dumped output data. And that tabulating the dump output in the database eliminates the need to know the column numbers of variables and opens up a rich set of tabulation capabilities built into the structured query language (SQL) select command. SQL is a declarative (rather than a procedural) language, so a user needs only to specify the nature of the tabulated table and then the SQL database figures out the procedural program that produces the specified tabulated table.

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

[codecov-io]

Codecov Report

Merging #1312 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1312      +/-   ##
==========================================
+ Coverage   99.65%   99.65%   +<.01%     
==========================================
  Files          38       38              
  Lines        2878     2890      +12     
==========================================
+ Hits         2868     2880      +12     
  Misses         10       10

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

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