More Python/pip package cleanup : version 2.0.17.

Generate astronomy.py directly in the package directory.
I realized it doesn't make sense to generate it in the
parent directory and then copy it; just generate it where
it will end up anyway.

Updated documentation so people know they can just do

    pip install astronomy-engine

to install Astronomy Engine in their Python project.

Removed the GitHub Actions status badge because it is redundant with
the checkmark/X indicator.

Now that private symbols are no longer exported, I had to
fix a couple of places where the unit tests still accessed them.

source/python/setup.py

@@ -2,7 +2,7 @@ from setuptools import setup
 
 setup(
     name='astronomy-engine',
-    version='2.0.16',
+    version='2.0.17',
     description='Astronomy calculation for Sun, Moon, and planets.',
     long_description=open('README.md').read(),
     long_description_content_type='text/markdown',