Doc adjustments

- Cleanup some grammar and adjust some wording usage.
- Add more docs to utils about what should and should
  not be used.
- Add more engine docs about how each one is used and
  tips and notes about each.
- Line length adjustments (might as well keep it somewhat
  in the normal range of what openstack code expects)

Change-Id: Ice6711f00e2b50e0bee777388c0555d79cc6e1b0
Merge "Doc adjustments"