Added trove backup section to user guide

The trove chapter in the user guide did not have
a section on database backup and restore.

This commit covers how to backup and restore a
database instance.

This commit is a partial implementation of the blueprint.

Change-Id: If0457f6205f3bb98eddd8c72d6c7afd1e6327712
blueprint: user-guide-trove-chapter
Merge "Added trove backup section to user guide"