Fixed bug in REFPROP upper case handling

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Added docs to C++ Props overloads

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Added JSON output to all helmholtz derivative terms; Changed Fluorine to use new formulation

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>