improved error message formatting
OpStreamingHdf5Reader: When readying hdf5 dataset dtype, use numpy.uint8 instead of numpy.dtype('uint8')
OpMetadataInjector: Cleanup and eliminate a needless copy.
implement cache memory usage diagnostics
delete old OpStackWriter
add lzf compression to big dataset writer
fixed bug in OpArrayCache: self.shape does not exist.
default cache operator report function raise NotImplementedError