Added docs for conversion of PlankEinstein and PlanckEinstein2 forms to generalized form

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
NBP reference states are now set

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Added passing tests for generalized PE term
Added failing tests for same reference state between REFPROP and Coolprop for enthalpy and entropy

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Fixed bug in Helmholtz energy Lemon2005 term (was using integer powers rather than the correct power)

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Added asserts for the lengths of the residual HE vectors loaded

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Fixed bug in Aly-Lee extend function (skipped new elements)

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Updated reference states for a few fluids

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Added tests for the reference states for fluids in REFPROP

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Implemented the Helium critical conductivity using REFPROP coefficients - relaxed tolerances on testing values due to uncertainty of origin of coefficients and other issues

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Relaxed viscosity at critical point to account for not using critical contribution to viscosity (same as in REFPROP)

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Fixed limit for R123 conductivity validation

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