Synnefo

webproject: common 404, 500 handling

- Move 404, 500 templates from astakos to webproject
- Remove 404, 500 templates from pithos-app
- Webproject now includes static files to serve jquery as an asset in 404, 500
pages.
- Custom 500 handler. Use RequestContext if possible.

Default configuration changes

- cached_db as default session backend
- removed default SITE_ID setting (not required by all synnefo
components)

Initial commit for snf-webproject

- new package snf-webproject
- moved basic django related settings in snf-webproject
- added new entry point utils to ease the extension mechanism of
snf-webproject (urlpatterns, middleware, static_files, installed_apps)...