richards box model: bring it to stable standards and fix its test

dumux/boxmodels/2p/2pfluidstate.hh

dumux/boxmodels/2p/2pfluxvariables.hh

dumux/boxmodels/2p/2pmodel.hh

dumux/boxmodels/2p/2ppropertydefaults.hh

dumux/boxmodels/2p/2pvolumevariables.hh

dumux/boxmodels/richards/richardsfluxvariables.hh

dumux/boxmodels/richards/richardsindices.hh

dumux/boxmodels/richards/richardslocalresidual.hh

dumux/boxmodels/richards/richardsmodel.hh

dumux/boxmodels/richards/richardsnewtoncontroller.hh

dumux/boxmodels/richards/richardsproperties.hh

dumux/boxmodels/richards/richardspropertydefaults.hh

dumux/boxmodels/richards/richardsvolumevariables.hh

test/boxmodels/2p/lensspatialparameters.hh

test/boxmodels/richards/grids/richardslens.dgf

test/boxmodels/richards/richardslensproblem.hh

test/boxmodels/richards/richardslensspatialparameters.hh