Don't merge, first commit of new event system, it's for preview only.

The brief of this design is at Google Document (https://docs.google.com/a/cocos2d-x.org/document/d/1rd59Ysp4R8iVelIDQmOOFAVQE8gek2bzBW_kPbTlnQc).

Please run `HelloCpp` of iOS and Mac to test.