The basic operators have been implemented in Grid2DObject and Grid3DObject as well as DEMObject (with the proper update strategy). 

In order to suppress the risk of out of date "ncols, nrows" and since these were redundant with Array2D<>.nx/ny, they have been suppressed and it is therefore now mandatory to rely on the getNx/getNy/getNz getters. This is much safer but impacted quite a lot of code...