fieldMinMax: add optional switch to control the output of max/min location

and simplify output format for graphing

With "location yes;"

log:
    fieldMinMax fieldMinMax output:
        min/max(mag(U.air)) = 0 28.309442
        min/max(mag(U.water)) = 0 27.221734

file:
    # Field minima and maxima
    # Time          min(U.air)      max(U.air)      min(U.water)    max(U.water)
    4.00061050e-01  0.00000000e+00  2.87015987e+01  0.00000000e+00  2.71025731e+01
    4.00134265e-01  0.00000000e+00  2.86505310e+01  0.00000000e+00  2.71134246e+01
    4.00222098e-01  0.00000000e+00  2.85937449e+01  0.00000000e+00  2.71255302e+01

With "location no;"

log:
    fieldMinMax fieldMinMax output:
        min(mag(U.air)) = 0 at location (-0.058373423 -0.15376628 0.021017389)
        max(mag(U.air)) = 28.701599 at location (-0.24002836 0.0053456235 3.8964638)
        min(mag(U.water)) = 0 at location (-0.058373423 -0.15376628 0.021017389)
        max(mag(U.water)) = 27.102573 at location (-0.24002836 0.0053456235 3.8964638)

file:
    # Field minima and maxima
    # Time          field           min             location(min)   max             location(max)
    4.00061050e-01  U.air           0.00000000e+00  (-5.83734226e-02 -1.53766281e-01 2.10173892e-02)        2.87015987e+01  (-2.40028359e-01 5.34562354e-03 3.89646377e+00)
    4.00061050e-01  U.water         0.00000000e+00  (-5.83734226e-02 -1.53766281e-01 2.10173892e-02)        2.71025731e+01  (-2.40028359e-01 5.34562354e-03 3.89646377e+00)