* 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

* eval in train

* add prune dygraph, test=dygraph

* fix slim readme and prune

* refactor rcnn, test=dygraph

* add mask_rcnn, test=dygraph

* add Faster RCNN & Faster FPN, test=dygraph

* update according to the review, test=dygraph

* fix feed var need prune when export

* fix format

* fix format

* add hrnet, test=develop

* add comment, test=dygraph

* move config file to hrnet, test=dygraph

* add 2x model

* add hrnet README

* update latest config structure, test=dygraph

* fcos infer

* fcos training

* fix stgraph fcosloss

* fcos doc

* fix dy_fcos

* add comment

* train eval deploy fcos

* remove fcos config, add comment

* fix iter_tic
Co-authored-by: Nnemonameless <nemonameless@qq.com>
Co-authored-by: Ngeorgenemo <nifeng@pku.edu.cn>

* add solov2 dygraph model, test=dygraph

* ppdet installable