Add service-list show `id` column

In nova this patch https://review.openstack.org/#/c/39998/ can show service's
id. Then user can use the id to delete service.

This patch support show service's id

Change-Id: I9fae88743ab7faea5e3fb64643f0bc9171e5b009
Implements: blueprint support-delete-service
Remove quota-class subcommand

quota-classes API was already removed.
  Change-Id: I1110022d6f628d03aaf363da707f2d2ef1600437
This patch removed quota-class subcommand from nova client.

Change-Id: I18bf7c255fabdb52c8ce8159f68c3e5c70e54993
Explain how to delete a metadata in aggregate-set-metadata

nova aggregate-set-metadata not given value of a key means delete the
metadata, so explain this usage in help message.

Change-Id: Ie8215bd8b47ed00e3d4686edab9e3052ae84774d
Merge "Add service-list show `id` column"
Merge "Remove quota-class subcommand"
Merge "Explain how to delete a metadata in aggregate-set-metadata"