This PR mainly does the following things
1、remove the cocos2d-x submodule, add download-engine.py to download the cocos2d-x engine, It can be configured in config.json.
2、modify the gaf, liquid, swiftTetris project property in ios and mac, add the iconv.dylib, because it's be used in cocos2d-x.
3、add MoonWarriors Sample
This PR mainly does the following things 1、remove the cocos2d-x submodule, add download-engine.py to download the cocos2d-x engine, It can be configured in config.json. 2、modify the gaf, liquid, swiftTetris project property in ios and mac, add the iconv.dylib, because it's be used in cocos2d-x. 3、add MoonWarriors Sample