anonymization values should be cognizent of types

Some anonymization values (such as below) should enforce properly formatted types.

For example, if an empty string is given for a numeric type, then it can not be inserted.  Currently the result is to set the attribute to have no value(s) at all, which is probably OK for most situations, but is not ideal.

    0018,1310 US 4  AcquisitionMatrix : 256 \  0 \  0 \  230

