Add documentation for the problem with CustomField encoders for mutable value objects, since we can't really do anything about it.

git-svn-id: https://j8583.svn.sourceforge.net/svnroot/j8583/j8583@73 db60a039-f72e-0410-b1d2-baa000846441

src/main/java/com/solab/iso8583/MessageFactory.java

@@ -178,6 +178,8 @@ public class MessageFactory {
 		if (templ != null) {
 			for (int i = 2; i <= 128; i++) {
 				if (templ.hasField(i)) {
+					//We could detect here if there's a custom object with a CustomField,
+					//but we can't copy the value so there's no point.
 					m.setField(i, templ.getField(i).clone());
 				}
 			}