- Modified order items survey controller to not accept data that can be obtained internally

- Customers controller won't throw any error on update if the date of birth submitted is the same as the one in the db already
Order item feedback controller will return an error if the customer has alread given feedback for the item
Order item feedback controller will return an error if the customer has alread given feedback for the item (code improvement)
Added more validation to the order item feedback controller
Fixes to index.php
Order items now return 4 new pieces of data:
- is_cancellable
- is_returnable_if_damaged
- is_returnable_if_buyers_remorse
- can_give_feedback