Reinstate differencing method info output

[ZedThree]

In versions <3 we had some output like:

    Setting X differencing methods
            First       :  Second order central (C2)
            Second      :  Second order central (C2)
            Upwind      :  Third order WENO (W3)
            Flux        :  Split into upwind and central (SPLIT)
    Setting Y differencing methods
            First       :  Fourth order central (C4)
            Second      :  Fourth order central (C4)
            Upwind      :  Third order WENO (W3)
            Flux        :  Split into upwind and central (SPLIT)
    Setting Z differencing methods
            First       :  FFT (FFT)
            Second      :  FFT (FFT)
            Upwind      :  Third order WENO (W3)
            Flux        :  Split into upwind and central (SPLIT)

In v4+ we now only print e.g. mesh:ddx:first = c2 and only when set by the user. It might be nice to have the previous information displayed.