* ppdet installable

* add christmas application

* fix element source

Old: PaddleDection
New: PaddleDetection
Although the title of the original article is wrong.

* support mask_rcnn for kunlun

* support faster_rcnn for kunlun

* Rename dir name in modeling

* Update changelog

Merge dygraph branch into master branch.
Co-authored-by: NFDInSky <48318485+FDInSky@users.noreply.github.com>
Co-authored-by: Nsunxl1988 <47514455+sunxl1988@users.noreply.github.com>
Co-authored-by: Nwangguanzhong <jerrywgz@126.com>
Co-authored-by: Nwangxinxin08 <69842442+wangxinxin08@users.noreply.github.com>
Co-authored-by: Nwanghuancoder <wanghuancoder@163.com>
Co-authored-by: Ncnn <liuhui29@baidu.com>
Co-authored-by: NGuanghua Yu <742925032@qq.com>
Co-authored-by: NKaipeng Deng <dengkaipeng@baidu.com>
Co-authored-by: Nroot <root@bjyz-sys-gpu-kongming0.bjyz.baidu.com>

* support ppyolo for kunlun

test=document_fix

* support mask_rcnn for kunlun

* minor

* update ppyolo_mobilenet_v3 large & small

* support visualdl in preprocess data

* support most preprocess op

test=document_fix

* update some link in README

* fix product news

* Update QUICK_STARTED_cn.md (#1757)

fix typo

* cherry-pick #1757 and #1473, test=document_fix

* update v0.5 release note

* update some comments

* add ppyolo_voc