[SQL] Allow more flexibility when parsing dates and timestamps in json datasources

object Precision extends Enumeration {
    val days, seconds, milliseconds, microseconds, nanoseconds = Value
  }

def convertWithPrecision(time: Long, from: Precision.Value, to: Precision.Value): Long = ...
...

  val dateFormat = parameters.getOrElse("dateFormat", "").trim
  val timestampFormat = parameters.getOrElse("timestampFormat", "").trim
  val longDatePrecision = getOrElse("longDatePrecision", "days")
  val longTimestampPrecision = getOrElse("longTimestampPrecision", "milliseconds")

      case (VALUE_STRING, DateType) =>
        val stringValue = parser.getText
        val days = if (configOptions.dateFormat.nonEmpty) {
          // User defined format, make sure it complies to the SQL DATE format (number of days)
          val sdf = new SimpleDateFormat(configOptions.dateFormat) // Not thread safe.
          DateTimeUtils.convertWithPrecision(sdf.parse(stringValue).getTime, Precision.milliseconds, Precision.days)
        } else if (stringValue.forall(_.isDigit)) {
          DateTimeUtils.convertWithPrecision(stringValue.toLong, configOptions.longDatePrecision, Precision.days)
        } else {
          // The format of this string will probably be "yyyy-mm-dd".
          DateTimeUtils.convertWithPrecision(DateTimeUtils.stringToTime(parser.getText).getTime, Precision.milliseconds, Precision.days)
        }
        days.toInt

      case (VALUE_NUMBER_INT, DateType) =>
          DateTimeUtils.convertWithPrecision((parser.getLongValue, configOptions.longDatePrecision, Precision.days).toInt