PRD3 schemas (was: [ubl] FW: Latest Spreadsheets)

[:]

| 4. ExtensionElement is now inserted in Maindocs and Namespace of
| the ExtensionSchemas is declared and imported.

msv raises consistent errors across the maindoc set:

   reference to the undefined element declaration: "UBLExtensions"

Same for xerces when run against the sample instances.

Jon