Besides removing unnecessary imports, this also fixes the missing logger module in test_architectures.py within the static directory.

* add static notice

* support mask_rcnn for kunlun

* minor

* update solov2 some detail

* fix check paddle version

* add enable_static()

* follow comments

* remove blank line

* unify log_smooth_windows and log_iter

test=develop

* remove duplicate log_iter

* remain mobile yml, since they are soft-link

test=develop

test=develop

* clean useless log in DataLoader

* fix infer set_sample_list_generator

test=develop

Add image for visualdl board.

* Update docs
* Update README.md

* optimize python path

* add yolov4

* update check config

* fix slim/xx

* Revert back to `fluid.clip` for gradient clipping

current API is in flux, wait for it to stabilize

* Please CI

still buggy

* add devices_num on reader

* refine capacity value

* refine bufsize

* 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).

* split yolov3 loss

* Polish Reader to simplify preprocessing logic.
#  sample_transforms-> make batch -> batch_transforms in Reader.
* Clean some code
* Imporve yolov3_r50vd_dcn_obj365_pretrained_coco 41.4 to 41.8.
* Update all configs.

* update code & doc

* Error out if fp16 is enabled and affine channel is used

* Add more documentation on mixed precision training

* add multi-scale test

This reverts commit b591cc133ca04dc1ed50631c8d24031bb97db18b.

* Add face detection configs and main code.
* Integration multi-scale evaluation.