$namespace = openstack.image.v{1|2}

The subcommand documents for $namespace were hardcoded and thus prone to
drift over time. This commit removes the hardcoded content and uses the
autoprogram-cliff directive to generate them automatically from the
subcommand configuration classes.

Some reorganization happened here. The `image` subcommand name is shared
by image v1 and v2. Previously the hardcoded document had them combined
and interleaved. Attempting to preserve this with autoprogram-cliff
would have required significant additional infrastructure. However,
since most readers care completely about one and not at all about the
other, we instead split the v1 and v2 versions of these commands into
separate pages. In case links to the old pages exist in the wild, they
are preserved, but moved (with redirects) to a hidden directory, and
populated simply with links to the new version-specific generated
documents.

Change-Id: I24dc6dc10671c7f1267c27002542f61f8a3c18ae

$namespace = openstack.identity.v{2|3}

The subcommand documents for $namespace were hardcoded and thus prone to
drift over time. This commit removes the hardcoded content and uses the
autoprogram-cliff directive to generate them automatically from the
subcommand configuration classes.

Special things:

- Some reorganization happened here. Certain subcommand names, such as
  `endpoint` and `project`, are shared by identify v2 and v3. Previously
  the hardcoded documents had them combined and interleaved. Attempting
  to preserve this with autoprogram-cliff would have required
  significant additional infrastructure. However, since most readers
  care completely about one and not at all about the other, we instead
  split the v2 and v3 versions of these commands into separate pages. In
  case links to the old pages exist in the wild, they are preserved, but
  moved (with redirects) to a hidden directory, and populated simply
  with links to the new version-specific generated documents.

- The `federation domain` and `federation project` subcommands were
  previously absent from the docs. They are added. These are such small
  commands and they seem related, so they're put into a single document.

- Some pages were already being generated but were listing operations
  individually instead of using wildcards (possibly because they were
  created before wildcarding was supported by cliff). These are changed
  to use wildcarding. (We want to do this wherever possible as it is
  more future-proof in the event that more operations are added to a
  subcommand later.)

- The `service provider` document was incorrectly titled `identity
  provider`. Fixed.

Change-Id: I2030f9fe370038c5908b6eb6bed9692a73fe5067

Use some regexes to reduce the number of lines in .htaccess and
hopefully make it slightly clearer which groupings of files redirect to
which new locations.

Also collapse one redundant double-redirect.

Change-Id: I65c4960856985d71076291f175df17f27a5ab8cc

Once [1] fixed plugin doc generation, the (single) page it produced was
unusably huge. This commit splits it into one page per project.

Note that there are four plugin projects that didn't have sections
included:

- cue
- murano
- tripleo
- watcher

These were noted in hidden rst which is preserved in the (new) index
page.

[1] Id9be39971110fd2eb4519a0582c9bf2514cdcacd

Change-Id: I0214ddb00a5a292a46d7cfb539d6dcc540fdae79
Story: #1735016
Task: #37239

Change-Id: I413a6d059f4eb751ca5c8b5a9b61740ac93680b1