Add CamVid format

[yasakova-anastasia]

Motivation and context

Add CamVid format support

How has this been tested?

Unit tests

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 increased (+0.03%) to 62.179% when pulling 7be7523 on ay/add-camvid into 240f07c on develop.

[nmanovic]

@yasakova-anastasia , could you please add missing annotation formats to https://github.com/openvinotoolkit/cvat#supported-annotation-formats table?