More robust Raoult's law methods

Updated the mixture saturation point functions to raise a runtime warning for each component that is supercritical.  Uses the shortcut correlation instead.

This allows the Raoult's law methods to be used for initial guesses even when the individual compounds may be outside their phase envelopes.

This both lets methods be more flexible and operate on real systems where in an ideal mix the compound would be supercritical and also removes some barriers that prevent attempts at calculations way outside the phase envelope for the mixture.