fix bugs in JSON input handling.
fix bugs in JSON input handling.

- the postgres `json_to_recordset` failed for JSON string fields like `"foo"`
- switch over to explicitly projecting fields from JSON input in SQL
- add special case for JSON columns to use `->` instead of `->>` projection

ini-bdds/ermrest,informatics-isi-edu/ermrest,ini-bdds/ermrest,informatics-isi-edu/ermrest