in order to announce readers and developers that the documentation source of PaddlePaddle.org has been moved to Fluiddoc repo

* slightly restructure the document [skip ci]

* Update dynamic_graph.md

* fix native_infer.rst

* fix the format

* new doc

* standard

* doc: append PADDLE_ENFORCE rules to new_op_cn.md

* doc: polish writing

* refactor: polish doc based on advice

* link IR graph to analysis graph

* add clean code and update

* add infer_clean_pass

* add ir_pass_manager

* support fc fuse executation

* fix ir circle

* hide misc APIs

* update

* fix transformer test

* update API.spec

Reduce one level of inheritence.

* Add Preface

* Add demo code

* Save file

* Refine code

* seems can work

* use elementwise strategy

* Use ElementwiseComputeEx

* Add comments

* extract functions from operator

* Refine code

* Follow comment

* code refine

* follow comments

* follow comments

add doc

* Add new_doc to develop branch

* Add pics of Anakin tutorial

* Update anakin_tutorial.md

* Delete anakin_fm_en.png

* Delete contri1.JPG

* Delete contri2.JPG

* Update build_and_install_lib_cn.rst

* Update compile_paddle_lib_cn.md

* Update compile_paddle_lib_en.md

* Update install_doc.rst

* Update install_doc.rst

* expose rank_loss python api

* Update index_en.rst

* Update index_en.rst

* Update index_en.rst