GitLab

* detr3d for dev-1.x

* update README

* clean redundant comments

* correct dir name 'config' to 'configs'

* Modified codes according to first round review

* Fixed grid_mask.py

* move detr3d_transformer.py to /layers

* reorganize files

* rename 'mmdet3d_plugin' to 'detr3d'

* Modify configs and update latest codebase

* rename configs

* forgot to save detr3d_head.py

* change data_root in configs

* try to fix lint

* correct config files

* reorganize dirs

* Fixing lint

* fixing lint

* fix lint

* Fix lint

* delete unused code

* rename configs

* delete transfrom_3d.py

* fix bugs in configs

* fix lint

* update readme

* edit config file

* rename detr3d/ to DETR3D/

* fix typos in readme

* polish readme

* fix config link in readme

---------
Co-authored-by: JingweiZhang12 <zjw18@mails.tsinghua.edu.cn>