David Culp:

David Culp:

Here's some new AI stuff.

1)  AI objects must now be defined in a scenario file, not in preferences.xml
or a *-set file.  (Of course this doesn't prevent objects from being created
dynamically, as with Durk's traffic manager).

2)  A new demo_scenario file is attached.  It creates 3 aircraft, a sailboat,
and a thunderstorm.

3)  Objects without flightplans live forever.

4)  FGAIShip::ProcessFlightplan() is not yet implemented.

5)  preferences.xml should now define only <enabled> and <scenario>