Add UnaryFunction subinterface
Added Copyable interface from scijava-ops
Added MetadataUtils
Let UnaryFunction implement Copyable
Added dependency of imglib2-metadata
Added UnaryFunctionTasks

UnaryFunctionTasks can be used for multithreading
Added HyperSlicer and AbstractHyperSlicer
Added default implementations of HyperSlicers
Added HyperSlicerService
Added HyperSliceProcessor
ImgPlusSlicer: make parameters private
HyperSlicingService: fix class hierarchy
Annotate concrete Op implementations with @Plugin