Sync config file generator from oslo

This commit syncs in the sample config generator from Oslo-incubator.
This will enable the sample file to be auto generated instead of
managing it by hand which is prone to errors.

Partially Implements: blueprint config-cleanup

Change-Id: Ic2553da72de5978b5d721d2ddb4c68ec1bf5005d
Merge "Sync config file generator from oslo"