Feat/flatten

[eXigentCoder]

Adds the new flatten command:

SELECT "First Name",
                    "Address",
                    flatten(Address,'Address_'),
                    unset(Rentals)
                FROM customers
                WHERE id=1

Results in:

{
          "First Name": "MARY",
          "Address": {
            "Address": "1913 Hanoi Way",
            "City": "Sasebo",
            "Country": "Japan",
            "District": "Nagasaki"
          },
          "Address_Address": "1913 Hanoi Way",
          "Address_City": "Sasebo",
          "Address_Country": "Japan",
          "Address_District": "Nagasaki"
}