Increased flexibility with the WayPoint class

Rather than forcing a GameObject to follow a single rigid sequence of locations, we can make things more flexible by defining a WayPoint class where each waypoint GameObject has an array of possible destinations, and each of these has its own array. In this way, a directed graph (digraph) can be implemented, of which a linear sequence is just one possible instance.

To improve our game and make it work with a digraph of waypoints, do the following:

1. Remove the scripted WayPointManager component from the Sphere-arrow GameObject.
2. Replace the ArrowNPCMovement C# script class with the following code:

 using UnityEngine;
 using System.Collections;

 public class ArrowNPCMovement : MonoBehaviour {
    public Waypoint waypoint;
    private bool firstWayPoint = true;
    private NavMeshAgent navMeshAgent;

    void Start (){
       navMeshAgent = GetComponent<NavMeshAgent>();
       HeadForNextWayPoint();
    }

    void Update () {
 ...