Gets the data for the selected row.
The row data is a JSON object of columnName:cellData key:value pairs.
The object only contains the data that is displayed in the table.
If the table is connected to a dataset, the rowData does not include the
fields from the dataset item that are not connected to table columns.
To retrieve the dataset item data that corresponds to the table row data,
use the dataset getCurrentItem()
function in the dataset onCurrentIndexChanged()
event handler.
Getting the rowData gets the same object that is returned in the array
of rows when reading the table's rows property.