Issue #2226: Improve Sprite, Node, LabelTTF class define for maintainability and performance
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-html5 into Iss2226_RefactorRenderingClasses

Conflicts:
	cocos2d/sprite_nodes/CCSprite.js
Closed #2226: Improve Sprite, Node, LabelTTF class define for maintainability and performance
Closed #2226: remove an unused variable "_opacity" from cc.LayerColor
Closed #2226: modify some comments
Merge pull request #1113 from dingpinglv/Iss2226_RefactorRenderingClasses

Closed #2226: Improve Sprite, Node, LabelTTF class define for maintainability and performance