Mode modifications to Box2d Generic Loader

[invaderwiz]

Modified the loader to comply with Cocos2d-x v3.2 and higher as seen here: https://github.com/invaderwiz/PhysicsEditor-Cocos2dx-3.2-Box2d-Generic-parser

Would be great if you had a look.

[mstorch]

There are a couple other ports to Cocos2d-x v3.x that I found at the following locations:

https://github.com/tks2shimizu/GB2ShapeCache-x-for-cocos2d-x-3.x
http://www.redtgames.com/blog/gb2shapecache-x-for-cocos2d-x-v3_2/

@CodeAndWeb, would you accept a pull request if someone submitted it for this generic Box2d physics shape loader (GB2ShapeCache-x.cpp/h)? The current version does not build.

Thanks,
Mark