Implemented basic highlighting of walkable tiles
Removed target/.gitignore (cargo now clears 'target' dir every build)
Added WeaponType and restructured Core constructor
visualizer/event_visualizer.rs: get_unit_scene_nodes(): Generic algorithm
Core: command_to_event(): Employed get_unit_type_id()
Pathfinder: limit move points (hardcoded)
visualizer/event_visualizer.rs: get_unit_scene_nodes(): Smaller circle