Updated voc.py in case error occurs when xml file contains self closing node <difficult/>.

* fix label_list for mot, add warnings

* add result txt format, test=document_fix

* fix readme of mtmct, fix paddle.disable_static, test=document_fix

* fix cfg, test=document_fix

* remove paddle api

* cherry-pick cfg modelzoo readme

* cherry pick modeling engine source

* cherry-pick deploy python mot

* fix problem of s2anet while deploying

* correct problem of s2anet TestReader

* add dota default category

* add frame_rate for mot infer video

* add doc of frame_rate for mot video infer, test=document_fix

* add python train time eval

* add mpii infer support

* mot video decode to images

* add infer_dir for mot

* fix export and unite pose infer

* remove task in mot source

* set image_dir

* update doc

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

add dark deploy supported, mpii deploy supported;

* 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

* decord video infer

* add video infer write results

* 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 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

* 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

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

* add ttfnet enhance

* add doc

* fix pafnet training