Update the setup doc with new steps and links

* Add some additional config to http config. I had to add these to get
  it to work
* Update the discovery image links to latest nightly, and reference that
  in the pxe config
Do not validate equallogic backends unless selected
these params should just be static values;

they don't change based on user inputs. Without this, we're
getting format errors when an array param has a value of
nil instead of []
Merge pull request #303 from bcrochet/fix_eqlx_validation

Do not validate equallogic backends unless selected
Merge pull request #304 from sseago/fencing-param-defaults

these params should just be static values;
Merge pull request #275 from bcrochet/setup_doc

Update the setup doc with new steps and links