astro/astrometry: Put python into versioned dir

The Python files and libraries were incorrectly installed under
lib/python instead of lib/python3.x and were therefore not version
specific. This was corrected by using PYTHON_LIBDIR.

While here, doing some more corrections:

- Use PY_BASE_INSTALL_DIR for PYTHON_LIBDIR
- Move DATA_INSTALL_DIR into MAKE_ENV
- Strip bin and lib files
- Remove PORTDOCS and PORTEXAMPLES entries
- Pet portclippy
- Update pkg-plist
- Bump PORTREVISION

MFH:		2022Q3