Fixed #2444 Re-write cc.Texture for Canvas Mode. Texture2D was used Image/Canvas instead on Canvas Mode , now rewritten it.

Conflicts:
	cocos2d/misc_nodes/CCRenderTexture.js
	cocos2d/sprite_nodes/CCSprite.js
	extensions/GUI/CCControlExtension/CCScale9Sprite.js
 Fixed #2444 Split  cc.Texture2D  as cc.Texture2DWebGL and cc.Texture2DCanvas
 Fixed #2444 Fixed bug that cc.PointZero use as a value ,but it is a function.
Fixed #2444 Fixed some bug about merged the code
Merge pull request #1067 from xingsenma/develop_texture2D

Refactor #2444: Re-write cc.Texture for Canvas Mode