added new sanity checks and compile-time assertions to prevent errors

fixed stair-building issue
new test-cases
added elevator support
fixed/improved some walker modules

grid/GridNode.h

@@ -18,6 +18,10 @@ template<typename> class Grid;
  */
 struct GridNode {
 
+private:
+
+	static int constexpr MAX_NEIGHBORS = 10;
+
 private:
 
 	/** grant full access to the grid */
@@ -27,7 +31,7 @@ private:
 	int _idx;
 
 	/** INTERNAL: store neighbors (via index) */
-	int _neighbors[10];
+	int _neighbors[MAX_NEIGHBORS];
 
 	/** INTERNAL: number of neighbors */
 	uint8_t _numNeighbors;
@@ -61,7 +65,7 @@ public:
 	int getNumNeighbors() const {return _numNeighbors;}
 
 	/** reached neighbor limit? */
-	bool fullyConnected() const {return _numNeighbors >= 10;}
+	bool fullyConnected() const {return _numNeighbors >= MAX_NEIGHBORS;}
 
 	/** is this node connected to the given index? */
 	bool hasNeighbor(const int idx) const {