Mention defaults subdirectory in a more visible way

Update playbooks_variables.rst

vsphere_guest module doc fix

All examples do not show it, so only someone reading the doc from
end to end would know about it.

Fix a bug causing yum module to not update to latest in some cases

Fix the docs for glance_image.endpoint_type

very small and minor addition, but I couldn't find anywhere that answered this (now obvious) question I had of whether or not facts could also be yaml files.

zypper: handle lists of packages efficiently

Fixes #8806

Fixes #8925

Fixes #7284

Tracebacks are now catchable with ignore_errors and have streamlined output.  Also removes 'baby-JSON' for bash modules.

Fixes #8971

Add missing tag to roles file example.

Correct mysql integration indentation

Rolling Instance Replace.  Fixes #8501.

Fixes #8968

Include el7 mariadb support in mysql integration test

Fixes #8813

Make it more likely folks will read this page :)

Also adds integration tests for booleanification of strings

Fixes #8629

Modules are almost always written now by mutliple authors, so don't show this field on website, since it grows obsolete and does not take into account all contributors.
Contributors are still listed on github module source and in repo, and original authors still in the file for when development questions arise, but want
to funnel support questions to the mailing list versus directly to them.