This PR refactors the code for reading trajectories, and add the following:
Allow platforms to be missing in the configuration. In this case, the platform is assumed to be located right above the first guide point, and it is assumed that there is no kickoff point.
Allow the kickoff point to be missing. Normally the kickoff point is prepended to the guide points, so in this case there is effectively only the guide points.
This PR refactors the code for reading trajectories, and add the following: