Product_import :product_nr is now a virtual prikey

If on import a product exists with the same product_nr,
update that product. Otherwise create a new product with the given
attributes.

Plus some styletweaks on the static_pages
Some cleanup and better styling
Subcategories and Layout tweaks

Beside a working subcategories design many changes on static pages
and assets and design (images, css, layout)
News module working and some more seeds

Many categories are pre seeded now.