Document configuration options

[timmycarr]

/kind feature

Describe the solution you'd like
Wardroom has many options for configuration of everything from certs to calico. Add documentation to show exactly what's needed and what knobs can be turned by configuration in the extra-vars.yaml I recently ran into a configuration problem with calico that could have been solved by finding the calico example file and realizing that I left out fields, but between that and other options (kubernetes version for example) it would be good to more clearly document this process.

Anything else you would like to add:

Environment:

• Wardroom version: branch:
• OS (e.g. from /etc/os-release):

[scottslowe]

@timmycarr Can you have a look at the changes in #200 and let me know what else you'd like to see documented?