Co-authored-by: NFeng Ni <nemonameless@qq.com>

* update README

* update doc, test=document_fix

* add citation

* update citation and ppyolo doc

* update readme en, test=document_fix

* update doc

* add 2.0 CHANGLOG

* add changelog history

* update doc

* notes for static -> dygraph

* move ssld model, test=document_fix

* fix typo, test=document_fix

* add s2anet

* add docs for custom dataset, reader and model technical

* modify docs according to review, test=document_fix

* modify READER.md, test=document_fix

* add config annotation doc, test=document_fix

* update doc of config

* mlp_dim-->out_channel of TwoFCHead

* update install doc, test=document_fix

* update doc, test=document_fix

* update doc, test=document_fix

* update doc, test=document_fix

* update quick_start

* update get_started

* update doc, test=document_fix

* Update install doc and deploy doc.

* fix dide link, test=document

* fix dide link, test=document

* support mask_rcnn for kunlun

* Rename dir name in modeling

* Update changelog

* support ppyolo for kunlun

* Update QUICK_STARTED_cn.md (#1757)

fix typo

* cherry-pick #1757 and #1473, test=document_fix

* update v0.5 release note

* update some comments

* Add PrepareData-->SelectModel-->Train-->Eval-->Test-->Infer-->Slim-->Deploy document DetectionPipeline.md, test=document_fix

* update solov2 some detail

* fix check paddle version

* enhance voc to coco docs

* fix voc annotation float type

* unify log_smooth_windows and log_iter

test=develop

* remove duplicate log_iter

* remain mobile yml, since they are soft-link

test=develop

* add PrepareDataSet.md, test=document_fix

* update PrepareDataSet, test=document_fix

* update PrepareDataSet, test=document_fix

* Update CN README
* Change demo and update doc

Repalce fruit dataset with roadsign dataset, and update QUICK_STARTED, use PP-YOLO as demo, test=document_fix. (#1407)

* add roadsign_voc dataset and update FAQ

* Add roadsign_voc dataset, updatea FAQ.md, and add yolov3_voc and yolov3_coco config template files.

* remove configs/templates

* convert config template file to md file, update comment

* mv config annotation file to config_annotation.

* move to docs/advanced_tutorials/config_doc

* rename

* update style

* update 2019-->2020

* update yolov3_mobilenet_v1_roadsign.md

* addd preprocess as yolov3_reader

* remove yolov3_mobilenet_v1_roadsign.md and add yolov3_mobilenet_v1.md

* fix typo

* update INSTALL

* fix typo

* add demo image

* add use_gpu annotation

* fix link

* update style

* update style

* add install paddle

* use python3

* update INSTALL_cn.md

* update INSTALL_cn.md

* update INSTALL_cn.md

* fix typo