The authentication docs for v3 were listing 20X http status codes as Error
responses. This commit corrects the documentation to list 20X codes as Normal
Docs at  have already been converted from WADL (SGML / XML) to RST
using fairy-slipper .
This commit polish the results from the conversion and migrate the docs
to our repository under 'api-ref/source' directory. In addition, it
added missing descriptions for access_token_id and consumer_id to
Polishing the generated RST files include:
- Removing unnecessary blank lines;
- Removing empty references.
Polishing the generated RST files do not include:
- Modifying their content;
- Modifying file names;
- Wrapping lines at the maximum of 79 chars.
Updating the documentation will be done after this migration step.
This change also adds a tox environment to build the docs using sphinx
under 'api-ref/build', which in turn is added to '.gitignore'.
Lastly, 'os-api-ref' is added as a test requirement. It provides the
sphinx stanzas rest_method and rest_parameter, used to define OpenStack
APIs in RST docs.