public static void TickToCompletion(this PathfinderEngine explorer)
 {
     while (explorer.State == ExplorerState.Working)
     {
         explorer.Tick(1);
     }
 }
 public static void ExploreToCompletion(this PathfinderEngine explorer, Coordinate from)
 {
     explorer.ExploreFrom(from);
     explorer.TickToCompletion();
 }