Change SQL version of Airports to use a larger field for the city name

[krlawrence]

Since the data set was first created several cities have been added that have a name longer than the 20 characters allowed by the VARCHAR(20) in the airports table. Sqlite3 seems to ignore this and create the values anyway but other stores such as Postgres throw an error.

gremlin> g.V().hasLabel('airport').filter {it.get().value('city').size() > 20}.count()
==>92  

gremlin> g.V().hasLabel('airport').filter {it.get().value('city').size() > 35}.values('city')
==>Sta Cruz de la Palma, La Palma Island

gremlin> g.V().hasLabel('airport').filter {it.get().value('city').size() > 35}.values('city').map {it.get().size()}
==>37