* add ppyolov2

* fix bugs and modify docs

* modify code and doc according to review

* fix bugs while resolving conflicts

* add PP-YOLO tiny

* add s2anet

* add pssdet model

* fix name of pretrain weights

* format, test=document_fix

* fix warning

* add senet

* add annotations according to review

* add Distill model

* add distill+prune

* refine ppdet file name

* unify bbox_utils

Co-authored-by: NGuanghua Yu <742925032@qq.com>
Co-authored-by: NFeng Ni <nemonameless@qq.com>

* 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>

* update ppyolo_mobilenet_v3 large & small

* update solov2 some detail

* fix check paddle version

* add enable_static()

* follow comments

* remove blank line

* add ppyolo mobilenetv3

* share train_batch_size from reader to model

* update floor_divide

* add makedirs for dumping config

* add solov2 model

* fix train batch size

* add solov2_r101_vd_fpn_3x

* fix batch size and update modelzoo

* refactor code of solov2

* fix deploy/python

* warning when YOLOv3Loss.batch_size setting

* add batch_size in YOLOv3Loss for backward compatable.

* sync TrainReader.batch to global train_batch_size

* fix deadlink in docs/tutorials/INSTALL_cn.md, slim/README.md and slim/extensions/distill_pruned_model/README.md