FlightGear 2.2 Support

I'm running FlightGear code from about mid-December, which is probably close enough to the upcoming 2.2 release to start building for 2.2. The B-17F project now has two versions, one for FG2.0, which I will no longer be working on, and one for FG2.2, which will continue to be developed. Eventually I'll have FG2.2 versions posted for all models.