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/Grid.h

@@ -108,9 +108,9 @@ public:
 	void connectUniDir(T& n1, const T& n2) {
 		Assert::isFalse(n1.hasNeighbor(n2._idx), "this neighbor is already connected");			// already connected?
 		Assert::notEqual(n1.getIdx(), n2.getIdx(), "can not connect node with itself");
+		Assert::isFalse(n1.fullyConnected(), "this node has already reached its neighbor-limit");
 		n1._neighbors[n1._numNeighbors] = n2._idx;
 		++n1._numNeighbors;
-		Assert::isBetween(n1._numNeighbors, (uint8_t) 0, (uint8_t) 10, "number of neighbors out of bounds!");
 	}
 
 	/**