Move the pythonhoted page to python_modules even though it is not
yet activated to render in the book.
Change location of pythonhosted md5sum ENTITIES to packages.ent
so they can be used in multiple pages but only need to be updated
in one place.
Note that pages not have entries like:
<!ENTITY asciidoc-md5sum "&asciidoc-md5sum;">
so this seems to be redefinig the entity to the version
in packages.ent. This seems to be OK with the build system.
