add keystone configuration instructions to manual install docs

[Doug Hellmann]

We need to update the documentation to include the step for configuring the API endpoint with keystone. Here's Julien's answer from https://answers.launchpad.net/ceilometer/+question/219904 that shows how:

You can take a look at how devstack does. Here is is:

keystone service-create --name=ceilometer --type=metering --description="Ceilometer Service"

keystone endpoint-create --region RegionOne --service_id $CEILOMETER_SERVICE --publicurl "http://$SERVICE_HOST:8777/" --adminurl "http://$SERVICE_HOST:8777/" --internalurl "http://$SERVICE_HOST:8777/"

Where CEILOMETER_SERVICE is the id of the service created by the first command, and SERVICE_HOST the host where the Ceilometer API is running.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/24468
Committed: http://github.com/openstack/ceilometer/commit/6bb6787c12bfbd8d35174aab8f1b62cb0d4d19a2
Submitter: Jenkins
Branch: master

commit 6bb6787c12bfbd8d35174aab8f1b62cb0d4d19a2
Author: Gordon Chung <email address hidden>
Date: Thu Mar 14 15:21:56 2013 -0400

    add keystone configuration instructions to manual install docs

    Change-Id: I50aed064580a715b741e4ecf6bb7e74bdcdfd514
    Fixes: bug 1104062