change the proof graph generation

    generate for a range of 2 of the robots we want to predict next_step
    use simple cases for the mask (3x3)
    add 2 'leftmost' cases : 1.1.3 and 1.2.1 rotated
mini refactor to mini perf improvement
chg: don't hardcode leftmost cases, filter them
fix gen_surrounding's nb_left (genericity)
fix graphs jpg and add detail of single
don't ignore doc/*.jpg