position_vector: class to work with distances from home in NEU
balloon_utils: remove position related functions

These functions are now handled by the position_vector class
colour_finder: restructured into ColourFinder class
fake_balloon: restructured into BalloonSimulator class
find_balloon: restructured into BalloonFinder class
balloon_config: add get_string, set_string methods
balloon_video: class to capture images and write video
balloon_strategy: integrate PositionVector