introduce dockerfile linting

[TomasTomecek]

• migrate all dockerfile checks from MTF over here

[phracek]

MTF checks are:

• test_maintainer_label https://github.com/user-cont/colin/blob/master/colin/checks/labels/maintainer.py
• test_release_label https://github.com/user-cont/colin/blob/master/colin/checks/labels/release.py
• test_version_label https://github.com/user-cont/colin/blob/master/colin/checks/labels/version.py
• test_com_redhat_component_label https://github.com/user-cont/colin/blob/master/colin/checks/labels/com_redhat_component.py
• test_summary_label https://github.com/user-cont/colin/blob/master/colin/checks/labels/summary.py
• test_run_or_usage_label https://github.com/user-cont/colin/blob/master/colin/checks/labels/usage.py

Dockerfile related tests:

• test_chained_run_dnf_commands colin checks if pkg_mgr calls clean all #68
• test_chained_run_rest_commands
• test_copy_files_exist
• test_helpmd_is_present https://github.com/user-cont/colin/blob/master/colin/checks/best_practices/help_file.py

Image related tests:

• test_all_no_docs
• test_docker_clean_all colin checks if pkg_mgr calls clean all #68
• test_installed_docs

[TomasTomecek]

This issue is about linting dockerfiles, none of that exists in colin yet, therefore I would untick all.

Thanks for the complete list, that's really helpful.

[TomasTomecek]

We should discuss the list from Petr.

[lachmanfrantisek]

Sorry, I resolved this automatically..