Support for Market-1501 dataset format

[yasakova-anastasia]

Motivation and context

Add support for Market-1501 dataset format
Depends on openvinotoolkit/datumaro#102, openvinotoolkit/datumaro#108 and openvinotoolkit/datumaro#114

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) 2021 Intel Corporation
#
# SPDX-License-Identifier: MIT

[nmanovic]

@yasakova-anastasia , there are some problems with tests:

    task.export_task(task_id, temp_file, dst_format,
  File "/home/django/cvat/apps/dataset_manager/task.py", line 749, in export_task
    task.export(f, exporter, host=server_url, save_images=save_images)
  File "/home/django/cvat/apps/dataset_manager/task.py", line 631, in export
    exporter(dst_file, task_data, **options)
  File "/home/django/cvat/apps/dataset_manager/formats/registry.py", line 37, in __call__
    f_or_cls(*args, **kwargs)
  File "/home/django/cvat/apps/dataset_manager/formats/market1501.py", line 23, in _export
    for item in dataset._data._source:
AttributeError: 'Dataset' object has no attribute '_data'

[yasakova-anastasia]

@nmanovic , this PR depends on openvinotoolkit/datumaro#102, openvinotoolkit/datumaro#108 and openvinotoolkit/datumaro#114, so the tests fail.

[zhiltsov-max]

This should not be done this way, use transform for this.

[yasakova-anastasia]

I couldn't find transform for this task. What should I use here?

[coveralls]

Coverage increased (+0.07%) to 75.843% when pulling b8c6551 on ay/add-market1501 into eb1cb83 on develop.

[zhiltsov-max]

In future, it would be nice to provide an option to choose the label. Maybe, we should check for and use the only existing label in the task?