add dark deploy supported, mpii deploy supported;

* support --eval for s2anet

* add spine dataset and config yml for s2anet

* add doc for s2anet

* update doc

* fix typo, test=document_fix

* add some comments, and update import

* add mot score to txt results

* fix mot install typo

* add epoch for deepsort

* fix paddle no_grad

* deploy infer save image txt

* remove mot metric

* lazy import motmetrics

* jde fairmot export and video python infer

* bs>1 for YOLO

* update slim models and benchmark

* fix config dependence & fix python 3.8/3.9 install

* add fairmot

* rename pretrain_weights

* add comments; reuse focal loss and convnorm

* update comments

* fix eval snapshot_epoch

* add config for jde and deepsort, add engine metric tools

* add mot_metrics

* fix configs engine and others

* fix configs others

* move configs

* fix ap_per_class, fix doc

* fix test_mode, seqs

* fix test_mode to metric

* fix JDE arch metric

* clean requirement

* add to requirement

* s2anet fix export and deploy

* remove redundant code

* fix cpp for s2anet deploy

* fix bug of get_categories

* rename poly_to_rbox to poly2rbox

* add some comment for function

* Add BottomUp HigherHRNet for pose.
* reverse xtcocotools to pycocotools

* Add S2ANet model for Oriented Object Detection.

* add Distill model
* add distill+prune

* refine trainer

* unity weights

* update tools/eval, support output_eval/json_eval

* update tools/eval, support output_eval/json_eval

* update tools/eval, support output_eval/json_eval

* update tools/eval

* remove load_static_weights

* add VisualDL and save best_model

* add VisualDLWriter callback

* Fix the bug of export quantized inference model

* Fix the bug of export quantized inference model

* add blazeface & update rcnn modelzoo

* remove condition num_priors

* use scripts to build on windows flatform, test=dygraph

* Use new preproces OPs in deploy/infer.py, test=dygraph

* fix bug of image_shape can not set 2-dims, test=dygraph

* fix cpp build, test=dygraph

* set param target_size must be [h, w] in Resize function, test=dygraph

* fix bug, test=dygraph

* fix ssd output format (bbox: [N, 6], bbox_num: bbox_num), test=dygraph

* fix ssd prediction in cpp mode, test=dygraph

* add fp16 and fleet api

* add instructions for fleet api and fp16

* modify example of fleet api

* modify docs of fleet api

* add ppyolo r18vd mbv3, yolov3 r50vd

* modify TestReader of ppyolo mbv3 r18vd

* add clip to avoid nan, modify ema to apply ema on bn mean and bn var

* fix code resulting in nan

* add yolov3 r50vd dcn configs

* finish yolo_series and fix some problems

* hide --bias flag and modify docs

* modify --bias and fix deploy/python/infer