A convenience method for extracting structured values from a DataBindingSource.
The method will look for all properties in bindingSource which have a key which
begins with propertyPrefix followed by an underscore and put each of those values
in the resulting Map with a key that matches the original key with the propertyName
plus prefix removed. For example, if propertyPrefix is "address" and
bindingSource contains the key "address_city" with a value of "St. Louis"
then the resulting Map will contain an entry such that the key is "city"
with a value of "St. Louis"
propertyPrefix - The property name to extract structured values for
bindingSource - the DataBindingSource to extract structured values from
A Map containing keys and values as described above.