PDF constructor is not protected against incorrect input

[johannct]

lephare/src/lib/PDF.cpp

Line 25 in 86fa1da

PDF::PDF(const double min, const double max, const size_t size) {

• nothing prevents argument size to be 0
• nothing prevents min>max in which case the xaxis is decreasing.

Note also that scaleLinear can be removed, as there is no use of it anymore.

[johannct]

@oilbert I do not think that there is any use for a decreasing xaxis