support stdout option

[mmacata]

When using ace, it would be nice to also have the stdout option available like so:

    {
      "id": "Select_number_hospitals",
      "module": "v.db.select",
      "inputs": [
        {
          "param": "map",
          "value": "zipcodes_wake"
        },
        {
          "param": "columns",
          "value": "ZIPCODE,number_hospitals"
        }
      ],
      "stdout": {"id": "number_hospitals", "format": "table", "delimiter": "\n"}
    }