This function allows one to add a keyed property to a molecule. The
key must be a string, but the value can be string, numeric or even an
arbitrary Java object (of class jobjRef)
Usage
set.property(molecule, key, value)
Arguments
molecule
A Java object of class IAtomContainer
key
A string naming the property
value
The value of the property. This can be character,
integer, double or of class jobjRef