dsOut = catObservations(dataSet1,dataSet2)
    Return a data set, dsOut, formed by vertically
    concatenating the observations, targets, and other fields
    in dataSet1 and dataSet2.
 
    Note that when dataSet1 and dataSet2 have different class
    names, and/or targets dataSet1 and dataSet2's className
    fields are used to generate a proper target/className
    representation for the output dsOut.
 
    As a result, the targets in the resulting dsOut may not
    exactly match the output of cat(1,dataSet1,dataSet2)