Merge pull request #6914 from andyque/refactorLayoutExecutant

refactor:  rename UILayoutExecutant to UILayoutManager
[AUTO][ci skip]: updating cocos2dx_files.json
Merge pull request #6917 from CocosRobot/update_cocosfiles_1401256188

[AUTO][ci skip]: updating cocos2dx_files.json
remove keyboard notifications from NSNotificationCenter
invalidate NSTimer instance in destroy to prevent memory leak
Merge pull request #6918 from minggo/fix-object-leak

Fix NSNotificationCenter and NSTimer leaks