Address Editor comments on Managing ProjectsUsers

* Adds a a caption to an image
* changes important tag to warning

Change-Id: I4b728be2fd7833e9475b32ba831f3464f5dd4821
Updates the Customize chapter to Havana.

Addresses O'Reilly editor comments. Better sematics for program listing,
screen output, and user input. Better formatting.

Change-Id: I664a1b086a913da144265f8843195320b7c9973e
Closes-Bug: #1257735
Merge "Address Editor comments on Managing ProjectsUsers"
Merge "Updates the Customize chapter to Havana."