User Definable CP Model

Let the user define whether to use a 2 point or
3 point model (Morton et al).

In addition, let the user define the interval durations
to use; by default we set to 3 and 30 mins.

For estimating CP against good, recent data both of these
models are more than adequate for the purpose.

We'll just keep kicking the can down the road whilst we
can rely on published, verified science.