Added trove config group section

The trove chapter in the user guide did not have
a section on how to use configuration groups.

This commit covers how to use config groups
to configure database parameters.

This commit completes the implementation of the
blueprint.

Edits for consistency - df

Change-Id: I749e7a1b0d2bfac799555844a15a99b24b46b7a2
blueprint: user-guide-trove-chapter
Merge "Added trove config group section"