Support gas dissolution in water (Rsw)

- adapt to interface change in waterPvt()
- add gas + water + disgasw simulator

Note
- MSW is not supported
- EQUIL initialization is not supported

opm/simulators/wells/SingleWellState.hpp

@@ -55,6 +55,7 @@ public:
     double thp{0};
     double temperature{0};
     double dissolved_gas_rate{0};
+    double dissolved_gas_rate_in_water{0};
     double vaporized_oil_rate{0};
     double vaporized_wat_rate{0};
     std::vector<double> well_potentials;