DataSelection: If the user selects a dataset that isn't valid for his workflow, automatically open the dataset property editor.
Resolves #433
OpThresholdTwoLevels: Output cache blockshape is only 1 pixel wide in the time dimension.
Fixes the second part of issue #416
adopted new calling convention for LabelImageViewerWorkflow init
Temporary operator instances are always initialized with parent, not graph.
widgets.ViewerControls: Update for recent ExportDlg api change.