New Audio Engine[ios/android]

Design Specification: https://docs.google.com/a/cocos2d-x.org/document/d/1aQdB16BkKyLBFg-DFVqhrZ5VWsf70eY0bbArEOycDoM/edit

The completed parts:2d audio on ios/android.
It is better to invoke `AudioEngine::remove()` though it will invoke `vector<>::find()` again.
But i think it is not frequently invoked, and reused codes is more important here.