* Update the optimization of PaddingRNN model in benchmark repo.

* Move the configuration of rnn model to a serapate file.

* Fix the error of forgetting feeding learning_rate when use py_reader.

* Add a argument and some check.

* Fix the feeding problem and remove some build options.

* Add some comments and refine the format.

* Fix an error when define the inference program.

* Remove the setting of use_experimental_executor, and simplfy some codes.

* Refine the setting of device_count.