fix h2 distribution in MultiphaseNonReflectingOutflowBCAlgorithm; fix negative phi in MultiphaseVelocityBCAlgorithm and in MultiphaseSimpleVelocityBaseExternalPressureLBMKernel; add unit test für FineToCoarseVectorConnector; redesign nozzle simulation setup

Corrected stress correction and a different way to implement the force externally from the kernel. Initial conditions for jet.

adds wrapper for gpu WIP

Now MultiphasePressureFilterLBMKernel pressure update is also corrected (wrong fiel in previous commit).