HEXAGONALGRID Generate hexagonal grid of points in the plane.

   usage:
   PTS = hexagonalGrid(BOUNDS, ORIGIN, SIZE)
   generate points, lying in the window defined by BOUNDS (=[xmin ymin
   xmax ymax]), starting from origin with a constant step equal to size.
   SIZE is constant and is equals to the length of the sides of each
   hexagon. 

   TODO: add possibility to use rotated grid

Package: matgeom