This exports all the old AIRFIELD_DATA to yaml files. It's easier for
users to send fixes if it's defined this way, and they can also fix it
in their install without having to wait for a new release.
This also switches the indexes from the unstable DCS airfield names to
airfield IDs, so this fixes another case of DCS updates occasionally
breaking Liberation.
I also ended up finding quite a few typos in airfield names, and
incorrect theater names in the process. Those have been fixed.
