* Categorize tools

* Update docs

* Rename tools

* Tool organization

* add onnx simplify option

* resolve comments

* add warnings

* Update documentation about the modification of train_cfg/test_cfg

* Fix docs str

* Add docs str

* Add docs str

* fix #4181, invalid link in readme for maskrcnn cityscapes

* undo

* Update customize_dataset.md

* Update config modification setting

* add doc for checking annotations of the new customized dataset

* reformat

* re-add docs for customized dataset

* Update customize_dataset.md

* use a cascase maskrcnn model as example to replace retinanet

* reformat

* reformat

* fix typo in doc

* update register

* also resolve #4334

* Add docstring for train.py/test.py/eval_metric.py

* Add docstring in the document

* Update docstring in the document

* Update docstring

* FPN deprecated warning

* FPN deprecated warning

* Update pretrain model url

* Fix pretrain model base url

* Add specific class pre-trained models

* Fix isort error

* Update doc description

* Update model url

* Rename config

* Rename config

* [doc]: add doc for pytorch2onnx

* [doc]: remove blank lines

* resolve format of doc

* refact doc for pytorch2onnx

* add space

* add to index.rst

* Add markdown lint in pre-commit hook

* add markdown lint

* bump to v2.7.0

* update dates

* update version requirements

* rephrase

* resolve comments

* update tutorials for changing training settings

* update

* Update details of hook

* resolve comments

* reformat

* Update module documentations

* add notes for classes specification

* add doc of modify loss

* minor fix

* change name

* update tutorials for changing training settings

* update

* Update details of hook

* resolve comments

* reformat

* add customize workflow

* clarify

* rephrase

* rephrase

* fix comments

Co-authored-by: Cao Yuhang <yhcao6@gmail.com>

* Fix tutorial

* small change

* Add custom_imports

* Add tutorial

* import import_modules_from_strings later to be compatible with previous mmcv versions

* support to evaluate concatenated dataset

* rm pdb

* update model zoo

* resolve comments

* Add assert during initialization

* more flexible usage

* add unittests

* change order of unittests

* Docs (new_datasets): update docs about concat dataset eval

* Docs (new_datasets): update docs about concat dataset eval

* Resolve comments

* Resolve comments

* Refine docs and fix format issues

* reformat

* fix mock

* Refine format

* Reorganize tutorials

* fix typo in docs and docstring

* update launch utility url

* add logo and resources folder

* update logo size

* change logo size to 400

* change logo size to 600

* clean legacy deprecated usage of register_module

* Update doc

`target_means` and `target_stds` should be in bbox_coder according to
https://github.com/open-mmlab/mmdetection/blob/2b6f6616f804beaca3dbf071fa398c586243db13/configs/_base_/models/mask_rcnn_r50_fpn.py#L48