A service for managing RichGauge instances.
The setValue method updates the current value of the gauge as well as incrementing the internal counter and updating
the max, min and average values.
It also provides a 'getOrCreate' method that will return an existing gauge given the name or create a new gauge set
to zero.
Supports a "smoothing constant", "alpha" for use in calculating an
exponential moving average for the
gauge.
The parameter can be changed at any time after the gauge has been created. The mean calculated up to that point will
be used to initialize the moving average from that point on.