Updating documentation for overview/details

Sahara communicates with the following services:
Heat, Cinder, Neutron and Ceilometer
These services are documented in rationale/details section.

Change-Id: I0d88397c02742e111b46ab525b489f8b8dbd29c4
Closes-Bug: #1350063
backport: none
Merge "Updating documentation for overview/details"