* add ext_op build doc, test=fix_document

* add note for JetPack version with machine

* update doc on develop, test=document_fix

* update dependency of ppdet and paddle, test=document_fix

* update docs, test=document_fix

* fix some docs error

* add ttfnet enhance

* add doc

* fix pafnet training

* move ssld model, test=document_fix

* fix typo, test=document_fix

* add ppyolov2

* fix bugs and modify docs

* modify code and doc according to review

* fix bugs while resolving conflicts

* update README

* update doc, test=document_fix

* add citation

* update citation and ppyolo doc

* add PP-YOLO tiny

* add pssdet model

* add senet

* add annotations according to review

* Add S2ANet model for Oriented Object Detection.

* update slim model

* fix skip quant

* add Distill model
* add distill+prune

* add fcos ttfnet coment, update modelzoo

* fix ttfnet coment

* update DataLoader & speed up Mask RCNN

* support not pad gt in rcnn model

* add comment in reader

* add ssd config file, test=kunlun

* revise file format

* support mask_rcnn for kunlun

* support faster_rcnn for kunlun

* support ppyolo for kunlun