The WPA Material loader should be able to use substances that have duplicate CAS numbers in WPA.

In WPA, substances with duplicate CAS Numbers are allowed so long as they have different substance

names or IMDS ID's.  However, we cannot load these substances onto a material using the material

loader because the material loader gives an error if it finds multiple substances with the given

CAS number in WPA.

What I'm proposing is that the material loader should have a field for the user to enter the IMDS ID,

and the logic of the loader should be changed in order to use a combination of CAS Number, Substance

Name, and IMDS ID to identify the substance rather than just using CAS Number.  Basically, the

loader should identify substances the same way WPA does.