Add the note of maximum microversion
Add the note of maximum microversion

On the gate, we are limiting each maximum microversion for stable
branches (Please see Id7ad136a4d79992e9df8d1aa463aff8fc58579ab as
the reference). For doing that, we are checking each project maximum
microversion for each release.
This additional note will help us, and the format is the same as
Nova's rest_api_version_history.rst.
In addition, this patch fixes some weird rst format.

Change-Id: I0f802fb4af5ded6186ab81ad28804b84824716e3

NetApp/cinder,phenoxim/cinder,eharney/cinder,Hybrid-Cloud/cinder,eharney/cinder,cloudbase/cinder,openstack/cinder,j-griffith/cinder,j-griffith/cinder,ge0rgi/cinder,openstack/cinder,NetApp/cinder,phenoxim/cinder,mahak/cinder,Hybrid-Cloud/cinder,Datera/cinder,Datera/cinder,mahak/cinder,cloudbase/cinder