Final round of edits for ch 1-3 before copyedit/index

- explain high availability
- revision to add paragraphs
- explain floating IPs
- remove server sizing bullet list that's repeated in table

Change-Id: I0cde4b85b99a5b05868251ea8f264cdc83994bb4
Merge "Final round of edits for ch 1-3 before copyedit/index"