*.xml, *.xsd: reformat using xmllint

Reformat the .xml and .xsd files using
	env XMLLINT_INDENT="    " xmllint --encode UTF-8 --format FILENAME.xml

Notable (non-whitespace) changes to the existing files:
- Ensure the <xml ...> header has encoding="UTF-8".
- <xs:schema ...> collapsed to one line and some attribute reordered.
- Empty tags are converted to self-closing tags. E.g.
	<xs:element name="Name" type="Type"></xs:element:>
  becomes
	<xs:element name="Name" type="Type"/>
- Some xmlns related attributes are reordered.

Per discussion with rapporteurs and Mark Canterbury.