Project import simple implementation

[ActiveChooN]

Motivation and context

This PR provides the whole dataset (data and annotation) import to the project function. In this iteration splitting data to the task just made by subsets and will be improved in future releases.

Resolves #2331, #1768

How has this been tested?

TODO Checklist

• Tracks support
• All formats import support
• Import status in UI

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

[bsekachev]

Could you please resolve conflict?

[bsekachev]

Subset "default" was created when import a dataset with not specified subset, then I exported the project and tried to import it again:

Probably not related with this PR, but if I reopen dataset export modal before the previous export finished, I see infinite scroolling. If it is easy to fix, maybe fix it? If not, I can submit an issue.

[bsekachev]

@ActiveChooN Please, take a look at tests

[ActiveChooN]

@ActiveChooN Please, take a look at tests

@bsekachev, fixed

[bsekachev]

Could you update cvat-ui version?

[ActiveChooN]

Could you update cvat-ui version?

Sure

[nmanovic]

@ActiveChooN , @bsekachev , I'm going to merge the patch today if I don't find any problems.

[nmanovic]

LGTM

[ActiveChooN]

@aschernov, could you please update the documentation?
@dvkruchinin, could you please prepare UI tests?

[dvkruchinin]

@ActiveChooN

could you please prepare UI tests?

Sure. A test will be prepared.