Implement software catalogue. Break the organisation object out as

part of the core, since it seems like it could be useful for other
kinds of objects as well in the future, but for now only the
software catalogue uses it.

pgweb/urls.py

@@ -29,6 +29,8 @@ urlpatterns = patterns('',
     (r'^about/quotesarchive/$', 'quotes.views.allquotes'),
     
     (r'^ftp/(.*/)?$', 'downloads.views.ftpbrowser'),
+    (r'^download/product-categories/$', 'downloads.views.categorylist'),
+    (r'^download/products/(\d+)(-.*)?/$', 'downloads.views.productlist'),
 
     (r'^docs/(current|\d\.\d)/(static|interactive)/(.*).html$', 'docs.views.docpage'),