* add yolov3 voc configs for dygraph

* simplify yolov3 darknet voc configs

* support num_classes shared from dataset config

* fix x2coco format problem

* 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

* refine dygraph config, test=dygraph

* fix fcos config