Moved the metadata into setup.cfg

[KOLANICH]

No description provided.

[KOLANICH]

@agriffis, @scls19fr

[agriffis]

@KOLANICH What does ths pull request do? I don't use Python on a daily basis any more, so I need more than the one line to understand.

[KOLANICH]

• Replaces metadata in a file with executable code with the same metadata in a file that is not executable code. This way
  • the metadata can be automatically read and patched;
  • the residual code calling setup is very simple and does nlthing else, and it is possible to write code detecting setup.py in this form.
• adds pyproject.toml - a relatively new standard for some metadata. It specifies a build backend for build - a new tool for building pythln packages. In fact it doesn't build packages itself, but calls other tools that are specified in pyproject.toml. It will be possible to move all the metadata from setup.cfg to pyproject.toml, but it is not closer than when setuptools implemented the pep.
• adds setuptools_scm that fetches version information from git tags. So no hardcoding it in the config files, also for non-tags commits a piece of hash is added, so if someone encountered problems, the precise version of the lib used is available in pip list. Since some version was hardcoded in source files for fast retrieval, I have configured setuptools_scm to create a file with version info in a form of source code.