Splitting Misorientation and Orientation into seperate files

[argerlt]

Description of the change

Extremely basic change. This is a blame-preserving and history-preserving split of the Misorientation and Orientation classes into separate python files. (ie, i used git -mv then re-merged branches)

This does not change the inheritance structure discussed in #345 , it just makes the orix/quaternions folder easier to navigate for new users.

Progress of the PR

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

Minimal example of the bug fix or new feature

>>> import inspect, os
>>> from orix.quaternion import Orientation, Misorientation

>>> # filepath for Orientation Class
>>> ori = Orientation.random(10)
>>> print(inspect.getfile(ori.__class__).split(os.sep)[-3:])
['orix', 'quaternion', 'orientation.py']

>>> # filepath for Misorientation Class
>>> miso = Misorientation.random(10)
>>> print(inspect.getfile(miso.__class__).split(os.sep)[-3:])
['orix', 'quaternion', 'misorientation.py']

For reviewers

• [x] The PR title is short, concise, and will make sense 1 year later.
• [n/a] New functions are imported in corresponding __init__.py.
• [n/a] New features, API changes, and deprecations are mentioned in the unreleased section in CHANGELOG.rst.
• [x] Contributor(s) are listed correctly in __credits__ in orix/__init__.py and in .zenodo.json.