add utils::findChildren()
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Merge pull request #7217 from CocosRobot/update_lua_bindings_1403752158

[AUTO]: updating luabinding automatically
[AUTO][ci skip]: updating cocos2dx_files.json
Merge pull request #7219 from CocosRobot/update_cocosfiles_1403764857

[AUTO][ci skip]: updating cocos2dx_files.json
Merge pull request #7218 from minggo/add-findChildren

Add utils::findChildren