pydown.py now searches description text for internal links
and expands them properly for Markdown file README.md.
For example: "#Body" ==> "[`Body`](#Body)".
Fixed a couple of incorrect "Astronomy_..." names in Python docs.
Never use pound-signs inside documentation for Python return types.
Automatically create internal link just like for function parameter types.
Added special case logic in pydown.py for "Time or `None`".
Fixed minor documentation mistakes in JS version.
In C code, replaced HTML italics with Markdown emphasis markers.
Added warnings for Python symbols with missing documentation.
Documented Python class Apsis.
Will generate different Markdown for my regular classes,
enumerated types, and error types.
Found out that 'from enum import IntEnum' pulls IntEnum
into the astronomy module and causes us to try to generate
documentation for it. Just keep it in the enum module.
Removed spurious dump of JavaScript README.md when verify_clean
fails.
I'm not going to use type annotations in function signatures
because they are causing more problems than they are worth.
The last straw was that different versions of Python don't
generate the same text representation. This broke my Travis CI
tests.
Once again, existing tools are too complicated and don't do what I want.
It's actually easier to create my own tool for this special purpose.
I also want the documentation to be similar in style to the other languages.
