Add contrib/json.arrai for working with JSON data

[orlade-anz]

The standard, canonical JSON structure is a pain to work with. In most cases the decoded data need not be reversible, and follows a schema that makes a tuple more appropriate than a map. This PR adds functions to apply these simplifications.

[coveralls]

Pull Request Test Coverage Report for Build 529f68a47d84b6e8b5380dfc5ac0406af4486df2-PR-616

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 48.091%

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Totals
Change from base Build 087fde7bcfa6240bcfcd245ee9185f42324aa3cc:	0.02%
Covered Lines:	4823
Relevant Lines:	10029

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💛 - Coveralls