Updated openstack/openstack
Project: openstack/ceilometer  7fb677e428d2616adcbd20b5f287f895c2360f83

Documented Stevedore usage and source details

Updated architecture document to mention Stevedore
and make a correct statement about polling frequency.
Updated configuration document to reference the relevant
section of the architecture document.
Documented the name parameter of the source stanzas in pipeline.yaml.
Documented the behavior when multiple source stanzas match one plugin.

Change-Id: I0d09f2bd8943425cd250574df41e77a68bdcf55e