* remove fields config in input_def

* add ssd_vgg16_120e_coco

* fix dygraph

* refine keep_ratio in ResizeOp

* replace RandomDistortOp with ColorDistort

* modify RandomDistortOp

* remove hsv_format

Co-authored-by: Nroot <root@bjyz-sys-gpu-kongming0.bjyz.baidu.com>

* adapt new im_shape im Mask R-CNN-FPN

* fix training

* split yolov3 loss using paddle op

* add sync_bn and modify list to LayerList to use sync_bn, add missing op, support cutmix op in dataset, modify reader to use new ops

* modify code according to review

* modify code to run eval.py successfully

* modify code to run eval and train successfully

* modify code to use mixup

* rebase code on lastest dygraph

* modify code to run in sync_bn mode

* modify code according to review

* modify target size of ResizeOp

* rename GridMaskOp to GridMask in ppdet/data/transform/operator.py to avoid conflict

* fix bugs in operator and batch_operator and check_version

* modify name in GridMask

* add comma according to review

* modify operators and batch_operators in data preprocess

* import BboxError and ImageError in operators

* modify code according to review

* modify some bugs

* add Gt2Solov2TargetOp in batch_operators

* modify code according to review