Draft: Dataset design docs

Explanation of changes

WIP for dataset design docs following up from #233 (closed). Feedback from there was incorporated and some new things have been added, namely the attributes specification.

I did not have time yet to create enough dataset examples to cover most of the specification, calibration points are one of the most important ones that is still missing.

If you wish to comment please do it in the docs/technical_notes/Quantify\ dataset\ specification.rst.py file, if you are curious why see comment below.

Please do not merge, contains unrelated features.

@AdriaanRol @dcrielaard @slavoutich

---

Merge checklist

See also merge request guidelines

• Merge request has been reviewed and approved by a project maintainer.
• Merge request contains a clear description of the proposed changes and the issue it addresses.
• Merge request made onto appropriate branch (develop for most MRs).
• New code is fully tested.
• New code is documented and docstrings use numpydoc format.
• Changelog has been updated (when applicable).
• CI pipelines pass
  • black code-formatting passes (gitlab-ci),
  • test suite passes (gitlab-ci),
  • no degradation in code-coverage (codacy),
  • no (serious) new pylint code quality issues introduced (codacy),
  • documentation builds successfully (CI and readthedocs),
  • windows tests pass (manually triggered by maintainers before merging).

---

For reference, the issues workflow is described in the contribution guidelines.