Put related entities into linked top level object
Code cleanup
Renamed STATUS_LOADED to STATUS_FETCHED
Move specialised logic for redirects to send() method.
re #91 : Handle redirects on failed actions

- Do not unset the referrer is the entity status is STATUS_FAILED.
- Set the status message if save/apply actions fails and provide a default if no status message exists.
- If the save action fails to not redirect to referrer but to current url.