permeable AlphaWall prgTotalPressure
New pair of BC for p_rgh/U for VOF. Works switching from prgTotalPressure/fixedFluxPressure following alpha.
Issue: updateSnGrad(snGradp) is called from pEq defined in constrainPressure.C. The search of BC is hard coded if BC is fixedFluxPressureFvPatchScalarField ,then updateSnGrad(snGradp).
In order to allow permeableAlphaWallprgTotalPressure to set snGradp, a new if else is needed asking if BC is permeableAlphaWallprgTotalPressure, then call updateSnGrad(snGradp).