Bug: E-bidirectional calculation systematic positioning error of an axis

There is an error in the script which calculates de error (bi-directional systematic positioning error of an axis) in the utilISO230_2.py.The mistake is to take the maximum of the minimum values instead of the minimum.

        x_i_avg_max=x_i_avg_fwd_max

        if x_i_avg_bwd_max>x_i_avg_max:

            x_i_avg_max=x_i_avg_bwd_max

        x_i_avg_min=x_i_avg_fwd_min

        if x_i_avg_bwd_min**>**x_i_avg_min:

            x_i_avg_min=x_i_avg_bwd_min