SolveGravityTurn:

 Solve for the initial conditions to perform a gravity turn trajectory.
  
  Iterate to compute the flight path angle perturbation (pitchover) to
  achieve a gravity turn launch trajectory that results in the desired
  flight path angle at burnout. Compare this ad hoc approach to the
  optimization performed in GravityTurnDemo.
  ------------------------------------------------------------------------
  See also RHSLaunchVehicle2D, MSThrustModel, RK4
  ------------------------------------------------------------------------