* upload activationsen.rst

* Update activationsen.rst

* Update activationsen.rst

* Review

* file path

* upload async_trainingen.rst

* Review

* upload cpu_train_best_practiceen.rst

* Review

* upload large_scale_sparse_feature_trainingen.rst

* Review

* sparse_update_en

* Review

* file path review x2

* conv_en

* Review

* Review

* optimizer_en

* Review

* file path

* tensor_en

* Review

* file path

* executor_en

* Review

* file path+review x2

* model_save_reader_en

* Review

* delete redundant

* inference_en

* Review

* upload sync_trainingen.rst

* Update sync_trainingen.rst

* Update sync_trainingen.rst

* Review

* upload mathen.rst

* Update mathen.rst

* Review

* file path

* upload /sequenceen.rst

* Review

* file path fix

* data_in_out_en

* Review

* Correct file path

* delete redundant

* programming_guide_en

* Review

Update layers_cn.rst

* upload cluster_train_data_en.rst

* Review

* polish

add explanation of auc

* control_flow_en_loss_function_en_metric_en

* Review x3

add explanation of auc

* upload memory_optimize_en.rst

* Review

* fix jargon

* Fix memory ==> video memory

* upload parallel_executor_en.rst

* Review

* Redundant

* Change api guides directory

* fix wrong ref

* Update memory_optimize.rst

* remove v2

* remove mobile

* check_1.3_api_update

* add launch mp distributed job

* fix comment

* update by comment

1. add index for all English version of "进阶使用"
2. replace legacy softlinks to howto/optimization & dev/new_op_en with original file

add gpu support

Remove paddle.v2

* host_memo_profile

* Update host_memory_profiling_en.md

* Review

test=develop

* upload write_docs_en.md

* Textual Review

* fix link ref

* upload op_notesen

* Review

* review2