Add API for posting user ratings

[mamadi]

• User can review different aspects of a spot.
• Individual ratings must be natural numbers between 0 and 5
• User ratings can be updated

[mamadi]

Added PUT API /ratings/:spot and documented it here

Sample PUT request body:

{"User": "Admin43", "Ratings": { "Wifi": 1.0, "Staff": 1, "Coffee": 1, "Seating": 2.0, "Parking": 1, "Overall": 1 } }