Doc for hough indexing with multiple phases

[Erlendos12]

Description of the change

Add documentation explaining how to do orientation refinemnet of crystal map with multiple phases from hough indexing.
For more information see #630.

Progress of the PR

• Docstrings for all functions
• Unit tests with pytest for all lines
• Clean code style by running black via pre-commit

For reviewers

• The PR title is short, concise, and will make sense 1 year later.
• New functions are imported in corresponding __init__.py.
• New features, API changes, and deprecations are mentioned in the unreleased
  section in CHANGELOG.rst.
• New contributors are added to release.py, .zenodo.json and
  .all-contributorsrc with the table regenerated.

[Erlendos12]

The notebook is currently just a copy of hough indexing with some minor adjustments, and a new "refine orientation" section at the bottom. I have created a PR (pyxem/kikuchipy-data#3) for the sdss data set, but do let me know if I instead should upload it to zenodo.

[review-notebook-app]

Check out this pull request on 

See visual diffs & provide feedback on Jupyter Notebooks.

---

Powered by ReviewNB