Revisit infiltration calculations

[martynpclark]

Infiltration is currently constant over a sub-step. Need to consider if infiltration should be included as part of the iterative solution. In subroutine soilLiqFlx.f90

[bartnijssen]

Need to revisit the parameterizations for infiltration and include parameterizations from existing models such as VIC to enable model mimicry

[wknoben]

Consider adding a new parametrization for soil crusting/hydrophobic soils