Address editor comments for ch7-networking (v2)

* Add a segue from intro to other topics, with
  a list of them and some kind of logical connection
* Define "Management Network"
* Give pool.ntp.org a name
* Add a conclusion
* Add Neutron Equivalent to nova-network Network Deployment
  Models table with additional introductory text.
Co-author: Anne Gentle
Change-Id: I0631b2ef9035c6041d34a9c3397367603f930fb3
Merge "Address editor comments for ch7-networking (v2)"