#14 XML input/output

[aric caley]

XML output can be done with a template set at first,
but it would be nice to have a more API like interface
where you could query for specific information in XML
(for, say, an affiliate site that just needs a product
list or whatever; or for a Flash frontend).

XML input could be used for exchanging data between
xshop sites, and as an easier way to create the initial
(or update) catalog. It would also make it easier to
update the xshop database schema as the XML format
would not change.

Someday we might even want to move to an XML database
entirely...