Comment 0 for bug 1640654

In the current api-ref, we have illustrated about how to add extra specs for flavors
http://developer.openstack.org/api-ref/compute/?expanded=create-extra-specs-for-a-flavor-detail#create-extra-specs-for-a-flavor
but it was very simple and we have a large number of built-in extra specs that can be
used to archive different purpose listed here:
http://docs.openstack.org/admin-guide/compute-flavors.html
The reader will still be confused about how to correctly use extra specs only read the
api-ref. We could first simply add the above link to the flavor extra spec section in
api-ref to let readers know where to find information and come up with better sulotion
later.