FIx some bugs in computing turnExitPos for fly-over waypoints,
and computing leg course when preceeeding leg is a runway.
In both cass we had an incorrect turnExitPos, so points along
the leg were incorreclty positioned.
Extend the test cases to cover this further.
Make the max-flyBy angle configuable, since for exmaple AIrbus uses 90
degrees. Expose this via a new gps/config property, and extend the tests
to verify that angles greater than the fly-by angle behav as fly-over
waypoints.
Extend the RoutePath code to share this configuration, so that route
visualisations match the configured angle.
SF-ID: https://sourceforge.net/p/flightgear/codetickets/2694/
GPS now lets the delegate handle the sequencing behaviour, by
setting a new config property. The default GPS delegate (in Nasal)
now sets this property.
This requires a corresponding FGData update.
