* 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

Fix the data file empty check.
Fix the utf8 file encoding.
Refine the README.

* Update transformer to be unified

* To support CE when unifing Transformer