[2p1cni] Port model and tests to next

dumux/porousmediumflow/2p1c/implicit/indices.hh

dumux/porousmediumflow/2p1c/implicit/localresidual.hh

dumux/porousmediumflow/2p1c/implicit/model.hh

dumux/porousmediumflow/2p1c/implicit/newtoncontroller.hh

...x/porousmediumflow/2p1c/implicit/primaryvariableswitch.hh

dumux/porousmediumflow/2p1c/implicit/propertydefaults.hh

dumux/porousmediumflow/2p1c/implicit/volumevariables.hh

dumux/porousmediumflow/2p1c/implicit/vtkoutputfields.hh

test/porousmediumflow/2p1c/implicit/CMakeLists.txt

test/porousmediumflow/2p1c/implicit/steaminjectionproblem.hh

...usmediumflow/2p1c/implicit/steaminjectionspatialparams.hh

test/porousmediumflow/2p1c/implicit/test_2p1c_fv.cc

...rousmediumflow/2p1c/implicit/test_boxsteaminjection.input

test/porousmediumflow/2p1c/implicit/test_ccsteaminjection.cc

...orousmediumflow/2p1c/implicit/test_ccsteaminjection.input