Replace the data/Airports/basic.dat.gz and data/Airports/runways.dat.gz with

Replace the data/Airports/basic.dat.gz and data/Airports/runways.dat.gz with
a single apt.dat.gz file which is in the native X-Plane format.

To do this I wrote a front end loader than builds the airport and runway
list.  Some of the changes I needed to make had a cascading effect, so there
are minor naming changes scattered throughout the code.