issue #4221 ccui.UIHelper->ccui.uiHelper
Merge branch 'develop-3.0' of https://github.com/cocos2d/cocos2d-html5 into develop-3.0-new

Conflicts:
	extensions/ccui/layouts/UILayout.js
	extensions/ccui/system/UIHelper.js
	extensions/cocostudio/action/CCActionNode.js
issue #4221 Correct gui constant
Merge pull request #1665 from xingsenma/develop-3.0

issue #4221 ccui.UIHelper->ccui.uiHelper
Merge pull request #1666 from SmallAiTT/iss_4277_fix4release3.0

issue #4277 : Refactor to reduce key words and fix some bugs.
Feature #4010: Add retina enable function
Merge branch 'develop-3.0' of git://github.com/cocos2d/cocos2d-html5 into develop-3.0
Merge pull request #1667 from pandamicro/develop-3.0

Feature #4010: Add retina enable function
Issue #4323： correct event manager jsDoc comments
Merge branch 'develop-3.0' of git://github.com/cocos2d/cocos2d-html5 into Iss4323_JsDoc
Merge pull request #1668 from dingpinglv/Iss4323_JsDoc

Issue #4323: correct event manager jsDoc comments
Fixed #4227: correct a bug in CCTIFFReader.js for advanced compile.
Merge branch 'develop-3.0' of git://github.com/cocos2d/cocos2d-html5 into Iss4323_JsDoc
Merge pull request #1669 from dingpinglv/Iss4277_FixBugsForV3.0

Fixed #4227: correct a bug in CCTIFFReader.js for advanced compile.
Issue #4277 : Remove some `on` functions of cc.game.
Merge branch 'develop-3.0' of git://github.com/cocos2d/cocos2d-html5 into iss_4277_fix4release3.0
Issue #4277 : Fix a bug while compiling by Closure Compiler.