Issue #2457: Merge webAudio and DOM Audio, Reduce the audioEngine logic

Test browser list:
Galaxy S4: Chrome, Firefox, WeChat, UC, oupeng, sougou, QQ, Baidu, liebao and System native browser
MI1S: Chrome, Firefox, UC, oupeng, aoyou, WeChat, Baidu, 360, QQ and System native browser 

Fixed ...
1. some browsers only allows the player to an audio
2. some browsers don't allow direct auto-play audio
3. Chrome 28 WebAudio playing multiple audio may feign death(android)
    ...

DOM Audio and WebAudio should unify - Share a Manager
Manager should not be mixed with compatibility code