Add metering configuration for nova

There are various attributes that need to be configured for nova to
start posting notifications for ceilometer to keep track of things.

This patch adds those attributes, and it additionally adds a single
property that can be set to automatically set them all on with sensible
defaults as described here:
http://docs.openstack.org/developer/ceilometer/install/manual.html

Change-Id: I99efbe0eef739afd62cde90d17578bbd83330c36
Merge "Add metering configuration for nova"