Added trove incremental backup section

The trove chapter in the user guide did not have
a section on how to do incremental backups.

This commit covers how to do incremental backups
and then use themm to restore a database instance.

This commit is a partial implementation of the blueprint.

Change-Id: I30080140147160c76fa1be09a1a2842d9a50e2a4
blueprint: user-guide-trove-chapter
Merge "Added trove incremental backup section"