i055: Sample RDDL document

Enclosed is a sample RDDL document (XHTML + RDDL extensions), for the
WS-Addressing namespace, illustrating how the namespace URI can be used
to provide a layer of indirection between a specification and the
schemas.

Just as W3C specs are versioned, this sample provides links to the
"latest" schema (subject to change through errata), and to dated schemas
which are frozen at a particular point in time.