* fix sync_bn in cpu

* fix voc eval

* remove debug code

* add comments

* update comment for collate_batch

* update ssd loss, make it faster test=develop

* update comments, test=develop

* ssd loss, fix bug when no object, text=develop

* pose bottomup higherhrnet: data
* mv common function to ppdet modeling;
* fix code style

* update 2.0.1

* refine yolov3 configs

* fix dataset problem

* add script of dota_2_coco

* add args for dota_to_coco

* add script to generate test result of dota

* add loss weight for s2anet

* fix dy2st for s2anet

* fix code style

* add ext_op build doc, test=fix_document

* add note for JetPack version with machine

* update doc on develop, test=document_fix

* update dependency of ppdet and paddle, test=document_fix

* update docs, test=document_fix

* remove rbox-iou-ops dependence

* update install doc

* fix some docs error

* fix name of ConvNormLayer for fcos solov2

* fix name in other head convbn

* fix yolo name, fix ttf_head name, test=document_fix

* update readme en, test=document_fix

* update doc

* add ttfnet enhance

* add doc

* fix pafnet training