add _className for Nodes
Merge pull request #1644 from wuzhiming/develop-3.0

Feature #4292:add property _className
Merge pull request #1645 from SmallAiTT/iss_4277_fix4release3.0

Issue #4277 : Change some apis to private.
Merge pull request #1646 from SmallAiTT/iss_4277_fix4release3.0

Issue #4277 : Add `bootFile` into `moduleConfig.json` to support `cocos2...
Issue #4277 : Make CCBoot to support singlefile mode.
Merge branch 'develop-3.0' of git://github.com/cocos2d/cocos2d-html5 into iss_4277_fix4release3.0