Handle the metrics sent by nova notifier

Nova compute node can now get metrics from monitors and send
notifications to message bus. So, add listeners to handle the
metrics in ceilometer. This patch changes the directory layout
for compute notifications, because there will be other metrics
(e.g. network and cache Qos) to be added. The deployer can also
add the metrics they want. It's better to make a classification
of these metrics.

Nova blueprint utilization-aware-scheduling

Change-Id: I6f54ef18035c437370360bbaff6d71666d0323fe
Merge "Handle the metrics sent by nova notifier"