[Data-modeling] Proposed changed to /aviation/airline_airport_presence

[Bryan Cheung]

The property cities_served on type /aviation/airline_airport_presence  
is a bit confusing. Is this disambiguating, non-reciporated property  
trying to describe the cities that the airline flies to from this  
airport? Or the city of the airport, which is then redundant with the  
serves property on airport?  This ambiguity also leads to some  
incorrect type assertions as some users add the airport as the  
destination city.  Perhaps the property should be destination  
airports, rather than cities.  What do people think?  The expected  
type of this property would be updated to /aviation/airport, and the  
property name would be updated to something along the lines of  
airports_served .

Bryan