use formatoptions.defaultValue during grouping if formatter is specified
use formatoptions.defaultValue during grouping if formatter is specified

One can change the behavior to old behavior by usaging `useDefaultValuesOnGrouping: false` in `groupingView` option.

Thanks @tlunven (https://github.com/tlunven) for the suggestion to implement the feature. See https://github.com/free-jqgrid/jqGrid/issues/288 for detailes.

javapark/jqgrid