Add utility functions, add units tests and package properly

[taldcroft]

Description

This does a few things. The scope expanded because I needed to update the package structure in order to add unit tests.

• Add get_sun_pitch_yaw and apply_sun_pitch_yaw functions
• Add unit tests. These are fairly minimal but better than nothing.
• Update setup.py and other infrastructure to modern standards.
• Put files into Ska/Sun/ instead of Ska/

Testing

• Passes unit tests on MacOS
• Functional testing

Functional test

pip install --user .
cd  # get out of repo
ipython --classic
>>> import Ska.Sun                                                                                                                                        

>>> Ska.Sun.__version__                                                                                                                                   
'3.6.1.dev6+g4303874'

>>> Ska.Sun.test()                                                                                                                                        
================================================================== test session starts ===================================================================
platform darwin -- Python 3.8.3, pytest-6.2.0, py-1.9.0, pluggy-0.13.1
rootdir: /Users/aldcroft/.local/lib/python3.8/site-packages
collected 7 items                                                                                                                                        

Ska/Sun/test_sun.py .......                                                                                                                        [100%]

=================================================================== 7 passed in 0.03s ====================================================================
<ExitCode.OK: 0>

[javierggt]

Looks good to me. I am assuming the functional tests are procedures you have used since before this change, right?

I would have put the test inside a tests directory, thinking of future additions, but no need to change it from what it is.

I also note that this PR requires sot/Quaternion/pull/36

[taldcroft]

@javierggt - I moved the test into tests/. Agreed that this is a more standard layout.

About the functional tests, I just made those up as a quick test to ensure that the packaging is right and the test infrastructure in __init__.py is working. This gives me good hope that the conda package build and subsequent skare3 testing will work, but I wouldn't bet my house on it.

After the update I re-ran the functional install testing and also confirmed that unit tests still pass.