worked on 3d models within map

adjusted grid factory
adjusted nav mesh factory
minoor changes/fixes
new helper classes
refactoring

grid/Grid.h

@@ -73,6 +73,11 @@ public:
 		hashes.clear();
 	}
 
+	/** is the grid empty? */
+	bool isEmpty() const {
+		return nodes.empty();
+	}
+
 	/** no-assign */
 	void operator = (const Grid& o) = delete;