Added trove chapter to user guide

The user guide did not have a chapter on how to use trove.

This commit covers the first topic in the chapter,
how to create and access a database.

This commit is a partial implementation of the blueprint.

Change-Id: I3824ae796c0c1d4175ef9fe6edc8f1cbe8d300f8
blueprint: user-guide-trove-chapter
Changed cluster to join_cluster in RABBITMQ

Changed the word cluster to join_cluster in
openstack high availability guide, subsection
configure Rabbitmq

Change-Id: I404b4e23da4c3b00dea65375fc76f72f19cb4b78
Closes-Bug: #1329340
Merge "Added trove chapter to user guide"
Merge "Changed cluster to join_cluster in RABBITMQ"