Revert "fix attribute namespaces"

This reverts commit ff3522d77af4212a9c4889172175b1d855a5a5bb.

We're going to fix this by removing the default namespace; it's cleaner.
fix element namespaces

The schema for XSD places elements in namespace
http://www.w3.org/2001/XMLSchema by default, but keeps attributes in no
namespace.  The placement of a default ns in the grammar element it
difficult to clearly distinguish these.

Remove the default namespace, explicitly qualify all element names, and
leave all attribute names unqualified so the ns attribute defaults to
the empty string per section 4.9 of the RELAX NG specification.