New test case for 2pncmin model added to dumux/test. For this following additional files are needed (Reviewde by Johannes)

- For variation of salinity in brine the needed constitutive relations are implemented in components brine_VerSalinity.hh and nacl.hh
- Additional constraint solvers (compositionfromfugacities2pncmin and computefromreferencephase2pncmin) are needed, specially for the case nPhaseOnly
- Additional constraint solvers (computefromreferencephase2pnc and miscible2pnccomposition) are needed for 2pnc cases in general.
- Fluidsystem brineairfluidsystem is updated
- Binerycoefficient file for brine_air case is included. 

- A test case for 2pncmin model is included for flusiong of precipitated salt in gas reserviors. The includes corresponding problem file, spatial parameters file, input file and *.cc file.
- For this the CMakeLists.txt is also updated.
- A reference solution 2pncmin test case "injectionbox2pncmin-reference" is included to test/references folder

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@15196 2fb0f335-1f38-0410-981e-8018bf24f1b0