elements README documentation environment variables should be clearer

[Augustina Ragwitz]

Per email discussion, element README.rst's should contain a sub section called Environment Variables with a Definition List where each entry is the environment variable. Under that environment variable we should have a field list with Required, Default, Description, and optionally Example. The goal of this change is to provide users a quick way to get the information they need, rather than the current state of having to sift through inconsistent unformatted text. This is also an opportunity to audit the README content to ensure it's up to date.

See the original thread here:
http://lists.openstack.org/pipermail/openstack-dev/2015-April/060867.html

[Augustina Ragwitz (auggy)]

I am currently working on this as individual commits per element, and also checking reviews that touch the README files.

[Augustina Ragwitz (auggy)]

I'm no longer working on this, if anyone else wants to pick it up, they can feel free.

[Augustina Ragwitz (auggy)]

Picking this back up!

[Augustina Ragwitz (auggy)]

Sounds like other folks are interested in this work. We should put together an etherpad to track what's been done and who is working on what, as well as any notes about bugs we've filed regarding redundancies.

[Jay_Clark (jay-clark)]

Decided to pick this one up. I've opened up an etherpad as @auggy suggested: https://etherpad.openstack.org/p/openstack-dib-1504632