Use metric dimensions as metadata in monasca collector
Use metric dimensions as metadata in monasca collector

With this change, a metric's dimensions are used instead of the measurement's
metadata for storage informations.

This allows the collector to provide more metadata and increases its performance
(less requests on the monasca API are made).

Change-Id: I1ecfe4929308718f9c448c5235634888dd456f3f

stackforge/cloudkitty,openstack/cloudkitty,openstack/cloudkitty,stackforge/cloudkitty