Added a function to check RPVersion - closes https://github.com/CoolProp/CoolProp/issues/305

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Remove the (char *) casts and take const char *

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Allow user to specify the REFPROP root path for fluids and mixtures

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Fixed handling of string configuration keys

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Derivatives are working, seems like a bug in REFPROP PHI0dll function is the only remaining problem

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Temporarily disable PHI0 until discrepancies can be resolved

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Implemented second partial derivatives in the AbstractState class

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Merge branch 'master' into refprop_derivative_support

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Converted REFPROP to use REDXdll to get reducing state (thanks to email from Eric Lemmon)

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Merge pull request #327 from CoolProp/refprop_derivative_support

Refprop derivative support