Moved SaturatedVolumicWeightOfCoverageLayer, DiameterD70 and DarcyPermeability properties from PipingInput to DerivedPipingInput. These parameters are not derived from the properties defined on soil layers in DSoil-Model. Made the parameters readonly in the property control. Added extension methods for PipingSoilProfile to be able to obtain collections of aquifer or aquitard layers. Updated DR6.soil demo data so that the layer materials define required properties for a calculation. Related to Issue [WTI-687] git-svn-id: https://repos.deltares.nl/repos/WettelijkToetsInstrumentarium/trunk@4465 5a3db67b-de53-47b5-99c8-a1c30a6650e2