Issue #4608: minimize the size of EventManager, Class, LoaderScene,Sprite
Issue #4608: use cc._addEventListener replace addEventLister
Merge branch 'develop-3.0' of https://github.com/VisualSJ/cocos2d-html5 into Iss4608_MinimizeCore

Conflicts:
	CCBoot.js
Merge branch 'develop-3.0' of https://github.com/VisualSJ/cocos2d-html5 into Iss4608_MinimizeCore
Issue #4608: add cc.clone to CCClass.js
Issuse #4608 Restore cc.ContentStrategy confusion