Build the framework

搭建游戏基本框架:
1.SceneManager控制场景切换;
2.PlayLayer游戏界面;
3.MenuLayer菜单界面;
4.BaseLayer背景层;
5.CreditLayer相关界面.

参考:[Cocos2d-x V3.x -- 开发进阶和高级实例教程](http://cn.cocos2d-x.org/tutorial/lists?id=52)