Reactivity weighting function customization

[ORNL-Modelica]

The effective fuel and moderator temperature weighting functions built-in to the subchannel models use the T_effective variable from the pipe model. The T_effective calculation uses mass weighted average (at least for moderator). Typically in kinetics calculations one uses a flux-weighted calculation. My suggestion would be to add a field for temperature weighting factors. The default could remain mass, or could be made powerProfile or powerProfile2 which are more typical.