- consistent with defining IO of int32_t/int64_t and with recent
changes to ensightFile. Using the primitives directly instead of
typedefs to them makes the code somewhat less opaque.
- centralises existing functions (erfInv, incGamma*, invIncGamma*).
Provides a location for additional functions in the future.
- adjusted existing models to use these functions
(e.g. distributionModels::normal)
