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