Add test master pattern to data module, IO notebook replace reST in user guide

[hakonanes]

Signed-off-by: Håkon Wiik Ånes hwaanes@gmail.com

Description of the change

• Continue migrating from reST to Jupyter notebooks in the user guide, this time the IO user guide page.
• Add 401x401 uint8 nickel master pattern at 20 keV beam energy in a modified version of EMsoft's EBSD master pattern file format returned by their EMMCOpenCL and EMEBSDmaster Fortran programs. The modifications are as follows:
  • Lambert and spherical projection intensities are rescaled from float32 to uint8 with kikuchipy.signals.EBSDMasterPattern.rescale_intensity()
  • A new HDF5 file is created with all groups and datasets of the original EMsoft HDF5 master pattern file, but with the projection datasets as uint8.
  • All datasets are written to the HDF5 file with kikuchipy.io.plugins.h5ebsd.dict2h5ebsdgroup compressed with gzip with compression_opts=9 (highest compression?).

Progress of the PR

• Docstrings for all functions
• Unit tests with pytest for all lines
• Clean style in as per black
• Finish notebook
• Finish setup of master pattern in data module

Minimal example of the bug fix or new feature

>>> import kikuchipy as kp
>>> smp = kp.data.nickel_master_pattern(projection="lambert", hemisphere="both")
>>> smp
<EBSDMasterPattern, title: , (2|401, 401)>

For reviewers

• Check that the PR title is short, concise, and will make sense 1 year
  later.
• Check that new functions are imported in corresponding __init__.py.
• Check that new features, API changes, and deprecations are mentioned in
  the unreleased section in doc/changelog.rst.

[hakonanes]

For some reason Readthedocs cannot push an update to this PR telling GitHub that the docs were built successfully as a check: https://kikuchipy--237.org.readthedocs.build/en/237/.

Edit: this now seems to work as expected.