Fix inplace saving in YOLO, CamVid and Cityscapes

[zhiltsov-max]

Summary

Related #348

• Renamed MaskCategories.make_default() to .generate(), added an option to include background color
• Fixed dataset patching in YOLO
• Fixed dataset patching in CamVid
• Fixed dataset patching in Cityscapes
• Updated Cityscapes implementation and documentation. Fixed Wrong saving mask *labelIds.png in Cityscapes dataset format #325, fixed Some mask files are not saved correctly when converting from VOC to Cityscapes #342.
• Fixed "background" class in Cityscapes colormaps
• Fixed Dataset.is_bound return value
• Added item presence check in DatasetPatch

How to test

Checklist

• I submit my changes into the develop branch
• I have added description of my changes into CHANGELOG
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues

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

[yasakova-anastasia]

This PR solves #342. I will close the PR #369.