- fix the SQLStore (make the connstring a connection, add tests)
- add tests for mem, file store
- fix the session problem, use cookie fallback if no session is given
- add SREG/AX/PAPE support
- make more configuration optional and provide default values
- rename sql_* to store_sql_* config options
- is came_from actually working?

- document logging
- document which errors can occur in self.error_field
