Python API documentation generation tool Code

- Generated HTML pages description updated.

- Fixed docstrings so they correctly link to the Epydoc API.
Currently it is required to use `register_canonical_role()` instead of
`register_local_role()` in `xlink.create_api_role()`

- Don't load duplicate entries in the URL generators.

- Always using the registered name to get the resolver, so it can work
as default role too.

- Using Epydoc logger to report index file parsing errors.
- More robust index file parsing.

- Added script apirst2html.py to the package.

- Added interpreted text directives to refer to external API.
- Epydoc HTML writer generates an index file suitable to be referred to.
- Added a script wrapping a Docutils HTML writer with external API reference
support.

- configuration file up-to-date with command line
- command line source code reformatted. Dropped those comments always
out of date...

- If there is no other info for a metadata variable, drop it as variable
- @newfield also add a metadata variable
- dropped __revision__ as alias for __version__. A new field can now be
defined.

- Documented the fact that consolidated list don't require the term
being interpreted text