As a user I want to be able to rate the restaurants

Tasks: 
- Add a new table “Cust_Location_Rating” for customer ratings
- Update the “Locations” table with values related to ratings
- Add a model “CustLocationRating” for the new table
- Add a UI element with 5 potato icons for showing average rating on the “imbiss” view
- Add a UI element for providing user rating on the “imbiss” view
- Modify the “rating” jquery for sending and showing the updated rating for a restaurant 
- Update the “Rating” controller with rateLocation function
- Make rating only possible for logged in customers