layer context menu: Export name defaults to layer name.
SubRegionRoiWidget: bug fix: Update roi on checkbox change.
Export file options widgets:
- Added stack export file options widget
- Adapted multiformat options widget to recent OpFormattedDataExport changes
- Added formatValidityChange signal, which uses op.FormatSelectionIsValid
DataExportOptionsDlg: Disable okay button if current format is not valid for the dataset properties.
export widgets: Cleanups.
StackExportFileOptionsWidget: Show a description of the files to be exported.