Several filter/convolution changes, nifty normalize8 Uint8ClampedArray trick.
Util:
	- normalize8: Return a Uint8ClampedArray, normalized to [.5,255.5]
	  then round/clamp to [0,255].  Solves subtle rounding/interval problems.
DataSets:
  - Added filter(f), applying f to each dataset element.
  - Added normalize8 dataset generator
	- Added blur, edge convolutions
	- Integrated util.normalize8