Added CSVRow to_json() method

[vincentlaucsb]

• Added CSVRow::to_json() and CSVRow::to_json_array() per Add ability to convert CSV Row objects to JSON #30
• Made CSVFormat interface more robust, i.e. errors thrown when user attempts to configure nonsense

[codecov]

Codecov Report

Merging #48 into master will decrease coverage by 1.64%.
The diff coverage is 96.52%.

@@            Coverage Diff             @@
##           master      #48      +/-   ##
==========================================
- Coverage   98.64%   96.99%   -1.65%     
==========================================
  Files          12       13       +1     
  Lines         663      766     +103     
==========================================
+ Hits          654      743      +89     
- Misses          9       23      +14

Impacted Files	Coverage Δ
include/internal/csv_row.hpp	95% <ø> (+0.26%)	⬆️
include/internal/csv_format.hpp	83.33% <ø> (ø)	⬆️
include/internal/csv_format.cpp	100% <100%> (ø)	⬆️
include/internal/csv_row_json.cpp	95.6% <95.6%> (ø)
include/internal/data_type.h	77.27% <0%> (-22.73%)	⬇️

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