* fix image_shape in export_model

* bs>1 for YOLO

* fix infer bug of s2anet

* update slim models and benchmark

* fix ffmpeg video infer, fix doc, test=document_fix

* fix ffmpeg installl, test=document_fix

* 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 inference benchmark

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

* Add S2ANet model for Oriented Object Detection.

* add Distill model
* add distill+prune

* refine trainer

* support not pad gt in rcnn model

* add comment in reader