[Seaside] XHTML support (Seaside2.7a1-pk.180.mcz)

[Pavel Krivanek]

Hi all,

I have changed the WAHtmlRoot initialization to support more general
way how to generate more types of documents in
Seaside2.7a1-pk.180.mcz. The document type, html attributes and head
attributes are now served by session so we may create XHTML pages
(with <?xml version="1.0"?>).

I have included simple counter application that includes embedded SVG
image (the code of the image is directly the part of the the generated
source code of the page). Not all browsers support this property now.

I had to change &nbsp; to more general &#160; because &nbsp; is not
valid XML entity.

Cheers,
-- Pavel