all SerialSlots listen for ValueChanged signals
opObjectExtraction operators use sig_value_changed
ObjectExtraction: Replaced OpLabelImage with the one from lazyflow.
ObjectExtraction: Refactored OpRegionFeatures to use OpArrayCache and use Output stype=ArrayLike
OpObjectExtraction: Use a compressed cache for object centers for much better performance.
PixelClassification: Comment.
BatchIo: Comment.
workflows: ObjectClassification: Minor cleanups.
ObjectClassification: Renamed OpToImage to OpRelabelSegmentation
ObjectClassification: Fixed two trivial crashes.
Implemented BlockwiseObjectClassification applet and workflow, which requires "normal" object classification applet to provide the classifier.
logging: Added blockwise object classification logger to config.