final concepts changes

Concepts is now ready for LC2


I have changed a number of the links:

updated Mime type registration link
changed undated W3C links to dated ones (e.g. to rdf-mt and syntax WD)
changed a link to XML schema datatypes to be more conventional in form.

changed a

http://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718.
to
http://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718/

Jeremy