probes: Improved formatting of header to make it easier to parse and read probe locations

New layout:

    # Probe 0 (0.0254 0.0253 0)
    # Probe 1 (0.0508 0.0253 0)
    # Probe 2 (0.0762 0.0253 0)
    #       Probe             0             1             2
    #        Time
            1e-05        142974        128861        115934
            2e-05      -69444.1        -62541      -56395.7
            3e-05      -1546.81      -1445.94      -1154.79