Consolidate subroutines in ThermalEnthalpySoilAux

The following subroutines should be consolidated:
```
ThermalEnthalpySoilAuxSetHeatCap
ThermalEnthalpySoilAuxSetThermalCondWet
ThermalEnthalpySoilAuxSetThermalCondDry
ThermalEnthalpySoilAuxSetThermalAlpha
ThermalEnthalpySoilAuxSetSoilDensity
```