PixelClassification: labeling op's deletelabel slot is broadcasted to all lanes.
ObjectExtraction: FeatureSelection dlg: layout resizes correctly.
FeatureSelection: Don't let the user click 'OK' if there are no features selected.  Also, indicate that the 'Raw Data' layer is for display only.
Fixes #682
DataExport: Close the results file (used in the on-disk view) when the export gui is hidden.
With recent lazyflow commit, this fixes #643
utility: Removed pathHelpers module, which is now in lazyflow
When using pathHelpers.getPathVariants(), always check if relpath is None.
DataExportGui: Cleanup print statements.