Added basic description and info for Orchestration.

Also included references to other guides and sections. Restructured a bit, using a 'Manage the OpenStack Environment' section, so that there aren't so many level-two headers in the CLI section.

Closes-Bug: #1267697

Change-Id: Ia717e2e8ef71154293a32dbfa7e80ebc8d00efda
Merge "Added basic description and info for Orchestration."