various changes to make URLs more context sensitive:

various changes to make URLs more context sensitive:

=over

=item *

the link fields for dyncart and the normal cart page are now always
generated as absolute URLs

=item *

the shop base pages are now always pregenerated as if the shop article
had an absolute URL, even when it doesn't.

=item *

the dynamic version of the url tag will now generate absolute URLs
when there is no article context and use the article link to decide
whether to generate absolute URLs in article context.

=back