Check that PDF::index behavior is really OK

[johannct]

lephare/src/lib/PDF.cpp

Line 335 in 86fa1da

if (inVal < scaleMin) {

I am not convinced that it is ok to peg the incorrect input into the first and last bin. In the case of pdf this is going to increase the discrepancy in the QQ plot for instance, while the input not being in the range of the grid should be considered as a cause of concern no? At least for the cases where the xaxis is redshift.