Add high-level function that allows for multiple outputs

[ibell]

I was thinking about a high-level function called PropsSIA (or something else), that would allow you to get multiple outputs in one shot, say H,S,P, if you give it T and D. I've had similar requests, and the REFPROP MATLAB wrapper includes this ability. Makes the high-level interface much more powerful, and avoids a lot of flash calls

[ibell]

See a40fee3