Add populating return event divs in main calendar,
Minor js changes in main calendar,
Remove product_code field from Product model.
Add editing of existing events.
Add cancel button to event creation and event edit.
Unify UX on all forms.
Minor authorization fixes:
- Fix authorization decorators,
- Make views use render instead of render_to_response to keep user data in context
Fixes and improvements for UX and db:
- move common js part for return events to one .js file,
- fix issue with db leftovers after clearing events during edit,
- fix issue with invalid vehicle_id when dragging vehicle over event