examples/*: re-order examples and make them consistent

[eparis]

Put the things people MUST set at the top (admin, baseDomain, name,
pullSecret.) And things people probably don't care about at the bottom
(CA, nodepools). Remove some things we don't want people to touch
(some networking options and the iSCSI block)

Hopefully it's just a little easier to find and set what matters.

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[wking]

@crawford mentioned plans to switch to the next-gen asset framework (cmd/openshift-install) this week, which would replace these examples with InstallConfig instances. And I have InstallConfig support in flight for the old framework in #236. The InstallConfig format isn't that different from the old YAML format, so we may still want some re-ordering, but if we do I'd rather handle it in #236 or the PR that switches us to openshift-install, just to keep the number of balls in the air down ;). On the other hand, it would be straightforward enough to rebase around this PR if we do want to land it now. Thoughts?

[eparis]

less work for me to close this, and redo after we land the change.