CXF generates XML schema. Sometimes it generates them wrong. It would be good if we could catch this.
For better or worse, XML Schema can't validate a schema. But Xerces can. We've seen this behavior from the version of Xerces inside the usual Sun JDK, but the SchemaFactory has no documented property to ask for this validation, and some other JDK might not have it. So, following the pattern of the (still unfinished, but progressing) StaX validation, I'm going to: 1) Make a new module that has a hard dependency on Xerces. 2) Cause it to register an extension on the bus if Xerces is really there. 3) Provide an API to validate a collection of schemas.
