* Update Transformer using Paddle-1.6 apis. (#3614)

* Update Transformer using Paddle-1.6 apis.

* Add check_version for Paddle-1.6 and reorganize utils including check, configuration, etc.

* mv neural_machine_translation to  PaddleMT (#3732)

* Paddle1.6 transformer fix (#3755)

* Revert "mv neural_machine_translation to  PaddleMT (#3732)"

This reverts commit a46365b6.

* Delete Transformer unremoved palm dir.

* Rename neural_machine_translation as PaddleMT.

* Update to PaddleMT in README.md

* Update transformer to be unified

* To support CE when unifing Transformer