add uri token; add dimension element

the uri token is used in the URI generation to be part
of the uri and identify the element itself, for instance
you have the URI http://localhost/ds/ec83...3ca/dim/e11a...a/:
it contains ds and dim as URI token which means, that there
is a certain dimension property (e11a...a) which is
related to a certain dataset (ec83...3ca)