setAdditionalField iterates over all entries

CreateNewProcessProcessor.setAdditionalField() was based on the
assumption that each entry in List ProzesskopieForm.additionalField
would exist at most once. This is not always true, and in this case only
the first occurence got populated. This fix seems to do it right now.
Merge pull request #1 from matthias-ronge/master

Bug fix for bug #1102401