Added representation of occupied squares and a way to retrieve them for A* implementation

Updated UML

src/Level.h

@@ -28,6 +28,14 @@ private:
     std::vector<Entity> entities;
 
     const TextureStore& textures;
+
+    //
+    // Pathfinding
+    //
+
+    std::vector<std::pair<uint8_t,uint8_t>> occupiedSquares;
+
+    Orientation findPath(sf::Vector2i start, sf::Vector2i end, int sign);
 };