XTCE12 — Calibrator selection using raw value

We use a piece-wise polynomial calibration to approximate the Steinhart-Hart equation for thermistor response.
That is, one polynomial is used when the temperature is low (and A/D counts are high) and another polynomial is used when the temperature is high.
The switch point between the two polynomial calibrators is expressed in raw A/D counts.

Using a ContextCalibrator (as currently defined) doesn't help as much as one would expect. ContextCalibrator context selection can use the raw value of a parameter instance (via useCalibratedValue=false) to determine context. The problem is that a specific parameter must be referenced in the match criteria; there is no mechanism to specify/reference generic input to the calibrator. This means we need to specify a separate parameter type for each thermistor parameter in order to specify the switch point. This creates an enormous amount of redundant declarations (the polynomials and switch points are identical for each parameter type, only the name of the parameter instance is changed) and somewhat circular logic (behavior of the parameter type is dependent on the parameter instance).

Should have a mechanism to directly reference the raw counts at the parameter type level.