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   Finds the optimal path using A*

   This function requires that you supply three functions

   cost  = PathCostFunction( startNode, goalNode, d.myData )
   cost  = TraverseCostFunction( node, newNode, d.myData )
   nodes = SuccessorNodes( node, parentNode, d.myData )

   Locations are denoted by an index. You use it in your functions
   to compute the costs.
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   Form:
   path = AStarSearch( startNode, goalNode, d )
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   Inputs
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   startNode (1,1) Id of start location
   goalNode  (1,1) Id of goal location
   d         (1,1) Data structure
                   .traverseCostFunction     (1,:) Name of traverse cost function
                   .pathCostEstimateFunction (1,:) Name of path cost function
                   .successorNodesFunction   (1,:) Name of path cost function
                   .myData                   (1,1) Data structure with your data
                   .nodes                    (1,:) List of nodes
                    

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   Outputs
   -------
   path      (1,:)  List of nodes in path 

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