* Fixup keyword dumping
* Clarify introductory text
* Turn links in the keyword description into seealso entries in the rst.
* Have plugin_formatter cleanup trailing whitespace
The indent filter in jinja2 < 2.10 indents blank lines by default which
leads to trailing whitespace. Cleanup after that filter.
* Edits
* Copy edit
(cherry picked from commit e07cbb033f)
* Use a rst glossary for playbooks_keywords docs
* Add a 'Task' and 'Tasks' to glossary.
* Update keywords desciptions,
* use :term: rst ref, some quoting
* Make it more obvious that 'retries' and 'until' need to be used in combination.
(cherry picked from commit 52f2edf19d)
