It can be quite nice to expose a basic set of metrics
about the internals of an engine, including the time
in each state, and how long the engine is active for
and likely more in the future.
To start add a engine statistics property and gather
some basic timing data and place this data into this
property for access (and/or introspection) by users.
Part of blueprint gather-engine-statistics
Change-Id: Ibc3c78755bd8ae779b52fc4772519f243a521576
97fd6660c6