Introduce cinder:config to manage custom options

This cinder::config is aim to use cinder config resources
to manage custom configurations in cinder config files.

This will make end user easy to add their own custom options
in Hiera data.

Fully implements blueprint cinder-custom-config

(cherry-picked from 9b40aa5692c82ce25c0127bea4567d9e62b51a52)
Change-Id: I58faf3f4c76b2eb2077552036a239b60103ee965