We recently came to the conclusion that the original idea how the
config options of Nova should be documented are too hard to maintain.
The discussion can be found on the ML starting with:
http://lists.openstack.org/pipermail/openstack-dev/2016-May/095538.html
This change reflects the outcome of the discussion.
Change-Id: I27b2cbb663f3c9a8c2503c3148280a3844f69cdd