add script to compute normals in using multiprocessing

[edgarriba]

this PR add a script to compute the surface normals using python multiprocessing

• add script with multiprocessing Pool and computes in parallel different maps
• add argparse to setup the data paths

[edgarriba]

achieved via pytorch vectorisation: https://kornia.readthedocs.io/en/latest/geometry.depth.html#kornia.geometry.depth.depth_to_normals