incorperate the review comments/decisions for multi-region PVT

the largest change is that all classes below opm/core/props/pvt take
the PVT region index as an argument, the higher-level ones (i.e.,
BlackoilProps*) take cell indices.

opm/core/simulator/EquilibrationHelpers.hpp

@@ -139,7 +139,7 @@ namespace Opm
                 props_.matrix(1, &p, &z[0], &c_[0], &A[0], dAdp);
 
                 std::vector<double> rho(np, 0.0);
-                props_.density(1, &A[0], &rho[0]);
+                props_.density(1, &A[0], &c_[0], &rho[0]);
 
                 return rho;
             }

opm/core/simulator/initStateEquil.hpp

@@ -369,8 +369,6 @@ namespace Opm
                                  const UnstructuredGrid&                 G    ,
                                  const double grav)
                 {
-                    typedef Miscibility::NoMixing NoMix;
-
                     for (typename RMap::RegionId
                              r = 0, nr = reg.numRegions();
                          r < nr; ++r)