[wip] add namespace support

This adds, basically, what I think will be needed to support xmlns stuff. I'm not sure where to put the flag to turn on xmlns processing, but it needs some kind of flag to replace the "TRUE" tests I've got in here.

Since I can't rely on <html xmlns=...> in every fluid document, and it would be difficult to add support here for the {namespace f=...} syntax, and this parser supports processor instructions <% %>, maybe I should have fluid add support for the syntax:
<%namespace xmlns=...%> or something like that. That way I can trigger adding the namespace in here.