Implemented all residual helmholtz energy terms

Signed-off-by: Ian bell <ian.h.bell@gmail.com>
Added remaining cases to eval function for residual base class

Signed-off-by: Ian bell <ian.h.bell@gmail.com>
More documentation for Helmholtz terms

Signed-off-by: Ian bell <ian.h.bell@gmail.com>
Fixed REFPROP density

Signed-off-by: Ian bell <ian.h.bell@gmail.com>
Removed function attribute from CachedElement.h

Signed-off-by: Ian bell <ian.h.bell@gmail.com>
reducing state uses molar units; can get pressure to agree with 4.2 values for water

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