added new helper methods

worked on gridWalker v3

grid/GridNode.h

@@ -64,6 +64,9 @@ public:
 	/** get the node's index within its grid */
 	int getIdx() const {return _idx;}
 
+	/** get the x-th neighbor's index within its grid */
+	int getNeighborIdx(const int x) const {return _neighbors[x];}
+
 	/** get the number of neighbors for this node */
 	int getNumNeighbors() const {return _numNeighbors;}