Support for providing namespace to use for fields of a Class (unless overridden by field)

Currently in the xml-module you have to qualify each field with the wanted namespace. This in many ways are similar to JAXB, but JAXB provides @XmlSchema for adding namespaces at the package level.

It would be nice if one could provide a default namespace for a class, so that theres not need to qualify every single field.

Even better would be to provide this at the package level, but class level should be more than ok for now.