* support no label training

* fix load_crowd

* update to fit rbox

* add empty_ratio

* update configs

* support mask rcnn

* clean drop_empty for mot & keypoint

* refine is_crowd

* fix mot_source

* fix mot_source, test=document_fix

* add video infer for TestMOTReader

* format, test=documment_fix

* add fairmot

* rename pretrain_weights

* add comments; reuse focal loss and convnorm

* update comments

* fix hsv randomaffine

* fix nms return_index

* fix gt_ide by tid_start_index

* add config for jde and deepsort, add engine metric tools

* add mot_metrics

* fix configs engine and others

* fix configs others

* move configs

* fix ap_per_class, fix doc

* fix test_mode, seqs

* fix test_mode to metric

* fix JDE arch metric

* clean requirement

* add to requirement

* s2anet fix export and deploy

* remove redundant code

* fix cpp for s2anet deploy

* fix bug of get_categories

* rename poly_to_rbox to poly2rbox

* add some comment for function

* add mot data

* fix operators, source

* fix data source transform

* fix parse_dataset register_op

* fix scale_factor, RandomAffine

* add assert for check

* fix ci

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

* fix voc eval

* remove debug code

* add comments

* update comment for collate_batch

* pose bottomup higherhrnet: data
* mv common function to ppdet modeling;
* fix code style

* add ttfnet enhance

* add doc

* fix pafnet training

* add pssdet model

* Add S2ANet model for Oriented Object Detection.

* add docs for custom dataset, reader and model technical

* modify docs according to review, test=document_fix

* modify READER.md, test=document_fix

fis the issue in function _get_shared_memory_size_in_M in the case of that there are multiple 'shm' space (#2434)

* update DataLoader & speed up Mask RCNN

* refine trainer