Bug # 1200325 - Updated CLI references from Quantum to Neutron

Updated all instances of Quantum in the CLI guide to Neutron. Added a
brief note in the overview under the table listing the clients to
indicate that the "neutron" client was previously known as "quantum".

Change-Id: I6ee94f4f56865d357ed1c1b11384f2a17c7c7cc9
Fixes: bug 1200325