REST API design based on our experience and popular articles

[nmanovic]

We should keep our REST API consistent. Just described general ideas behind the current REST API of CVAT.

Motivation and context

To prevent typical issues when people try to add new endpoints into our REST API.

How has this been tested?

N/A

Checklist

• I submit my changes into the develop branch
• I have added description of my changes into CHANGELOG file
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues (read github docs)
• I have increased versions of npm packages if it is necessary (cvat-canvas,
  cvat-core, cvat-data and cvat-ui)

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.
• I have updated the license header for each file (see an example below)

# Copyright (C) 2020 Intel Corporation
#
# SPDX-License-Identifier: MIT

[coveralls]

Coverage decreased (-0.02%) to 62.811% when pulling 9ebc264 on nm/rest_api_design into a9b2817 on develop.