zeros_like, ones_like

We often want some blank images to do stuff. Do you think it could be nice to have pyotb.zeros_like and pyotb.ones_like instead of this kind of hack?

exp = "{" + (nbands * "0;")[:-1] + "}"  # equals "{0;...;0}"
zeros_raster = pyotb.BandMathX(il=reference_raster, exp=exp)