* Make external links translatable.
If we use a separate-style of external links, link labels cannot be
translated, as they are used as label IDs.
* The new openstackdocstheme add version number on the left-top corner.
However, I18n project has no release, so the version, so the version
number has no meaning. There is no need to specify 'version' in
doc/source/conf.py.
Change-Id: I92c91bc39a079be2833a22527683b9c8bc477324
c2026ab88c