* add gcnet model : https://arxiv.org/abs/1904.11492

* Add GIOU loss.
* Add DIOU/CIOU loss.
* Change loss box type in bbox_head.py.
* Remove fuse_elewise_add_act_ops flag in train.py (Error may happen for elem_divbased on the flag).

* add res2net model

* modify yml files

* add res2net model zoo

* add hrnet model

* modify model zoo

* minor fix readme

* update readme in dirs

* minor fix softnms bug

* refine model zoo

* modify yml files

* modify pretrain names

* Add cascade_rcnn_cls_aware_r200_vd_fpn_dcnv2_nonlocal_softnms model on oidv5 and obj365.
* Add obj365 config annotation
* Update docs.

* move path to PaddleDetection repo in docs

* refine README

* add softnms, nonlocal, resnet200_vd_backbone
* add CBNet
* update model zoo

* update code & doc

* Update PaddleDetection/README_cn.md
* Follow comments
* Small update

* Add benchmark (fps) in MODEL_ZOO doc

* add gn doc

* update model zoo doc

* Add cascade deformable mdoels
* Fix MODLE_ZOO.md

# Add VGG-SSD on VOC and COCO dataset.
# Add config and model zoo. 
# Refine bbox2out and draw_bbox:
    - Add bbox de-normalize in bbox2out function.
    - Remove bbox de-normalize in draw_bbox.

* update doc in PaddleDetection

* add deformable models
* fix dcn v2
* fix log_iter

* fix cn docs

Add PaddleDetection docs & some model configs