CSV files with orientations:
- Added Trajectory.h that describes a trajectory of positions and orientations.
- TrajectoryCSVWriter (formerly csvwriter) now uses this new Trajectory type. Thus, UMANS now adds agent orientations to CSV output.
- Added TrajectoryCSVReader as well, to read a CSV file or a folder of CSV files. It is currently not used, but it may be useful in the future.
Closes #91 (closed)