Merge pull request #1564 from pandamicro/develop-3.0

Refactor #4028: Refactor labels extended properties getter/setter
Refactor #3878: cascadeColor getter/setter defined and refactored for cc.NodeRGBA & cc.LabelBMFont
Refactor #3963: cc.Layer extended properties getter/setter defined
Refactor #3878: Refactor cc.NodeRGBA extended getter/setter in engine
  opacity
  opacityModifyRGB
  cascadeOpacity
  color
  cascadeColor
Refactor #3963: Refactor cc.Layer extended getter/setter in engine
  remove blendFunc getter/setter
Merge branch 'gettersetter' into develop-3.0

* gettersetter:
  Refactor #3963: Refactor cc.Layer extended getter/setter in engine   remove blendFunc getter/setter
  Refactor #3878: Refactor cc.NodeRGBA extended getter/setter in engine   opacity   opacityModifyRGB   cascadeOpacity   color   cascadeColor
  Refactor #3963: cc.Layer extended properties getter/setter defined
  Refactor #3878: cascadeColor getter/setter defined and refactored for cc.NodeRGBA & cc.LabelBMFont
Merge branch 'develop-3.0' of https://github.com/cocos2d/cocos2d-html5 into develop-3.0

# Via dingpinglv
* 'develop-3.0' of https://github.com/cocos2d/cocos2d-html5: