Morphological operations: add the diamond strel, with optimization in 2D.

Optimization follows logratihmic decomposition in  Rein van den Boomgard
and Richard van Balen, Methods for Fast Morphological Image Transforms
Using Bitmapped Binary Images, CVGIP: Models and Image Processing, vol.
54, no. 3, May 1992, pp. 252-254.

So far it works in 2D. I will have to extend it so that it works at
least in 3D.
Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
Merge branch 'morphologyops' of git://github.com/imagej/imglib into morphologyops

Conflicts:
	algorithms/core/src/main/java/net/imglib2/algorithm/morphology/StructuringElements.java

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>