mpnc does not work with brineair fluidsystem

If the brineair fluidsystem is used with the mpnc model you get a singular matrix immediately. The 2pncmin/nonisothermal test works using the brineair fluidsystem and the 2pncmin model. On the branch fix/mpnc-with-brineair you can find this test now using the mpnc model. Here the mineralization part is removed. On the branch fix/mpncmin-with-brineair the test is using a mpncmin model. In both cases a singular matrix is obtained immediately.