DataDictionary doesn't preserve the "required" attribute of header/trailer fields

DataDictionary.load() method currently hardcodes all the header/trailer fields to be "not required".
As a result, even validating a message without a BeginString or SenderCompID passes, even though those fields are obviously required in the FIX dictionary file.

Source example:
String required = "false";
addHeaderField(lookupXMLFieldNumber(document, name), required.equals("true"));

Need to behave the same as with regular fields.