* add flag files

* add flags file

* delete space

* modify write_docs_cn, write_docs_en, include specifications about python 2.7.15 and creating  virtual env with conda

* gitignore update

* revert .gitignore;  update write_docs

* add python inference api doc

* Polish executor doc

* split layers,test=develop

* split nn layers

* remove nn header, test=develop

* new python op doc,test=develop

* fix typo, test=develop

* modified lrn formula

* modified design idea

* Update fluid_design_idea.md

* Update fluid_design_idea.md

* add contribute faq

* refine with comments

* Add the description of the quantization-aware training model format.

* add the abstract.

* Add lod specs

* Update op notes

* Update lod specs

* add infer shape

* fix bug

* fix example; test=develop

* fix language; test=develop

* fix format error

* fix error

* fix error

* update en api doc

* update Paddle commitid

This reverts commit 76d8f574.

* update_faq

* revise the style

* modify the FAQ format

* update_releasenote_0428

* add new

* update_commitid_Paddle_0428

* run gen_doc

* fix_table_link

* fix en

* fix typo

* Update native_infer.md