* save infer results to file.

* update, for mac temp file

* update func name, fix mem, fix dir

* add multi-scale test

* add resnet34-fpn-mstest item in model zoo

* support --eval for s2anet

* add spine dataset and config yml for s2anet

* add doc for s2anet

* update doc

* fix typo, test=document_fix

* add some comments, and update import

* Add BottomUp HigherHRNet for pose.
* reverse xtcocotools to pycocotools

* fix voc eval

* remove debug code

* add comments

* update comment for collate_batch

* refine trainer

* update tools/eval, support output_eval/json_eval

* update tools/eval, support output_eval/json_eval

* update tools/eval, support output_eval/json_eval

* update tools/eval

* add VisualDL and save best_model

* add VisualDLWriter callback

* add blazeface & update rcnn modelzoo

* remove condition num_priors

* 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

* refactor rcnn, test=dygraph

* add mask_rcnn, test=dygraph

* add Faster RCNN & Faster FPN, test=dygraph

* update according to the review, test=dygraph

* add solov2 dygraph model, test=dygraph

* ppdet installable