remove all export method of metas (cocos#2851)

Update version and fix small issues (cocos#2809)

* Update version and fix small issues

* Fix issues reported by gcc

Merge branch 'v1.9'

Merge branch 'v1.9-release'

Fix issues (cocos#2608)

* Add missed vec3 APIs

* Fix Node property setter issue

* Fix scene dirty sync issue

* Fix setWorldRot not setting dirty issue

update version to 1.6.0