Add an option to unquote embedded JSON

[matt4biz]

Remove extra quotes around {} and un-escaping quotes on strings

$ envy add test a='{"one":{"a":"1","b":"2"},\n "two":{"a":"5","b":"6"}}'

which would normally be output as

{"a": "{\"one\":{\"a\":\"1\",\"b\":\"2\"},\\n \"two\":{\"a\":\"5\",\"b\":\"6\"}}"}

now becomes

{"a":{"one":{"a":"1","b":"2"}, "two":{"a":"5","b":"6"}}}