The pvt interface is extended to handle wet-gas systems:
1. rvSat is added as a function in the PVT interface
2. SinglePvtLiveGas computes the pvt values and its derivatives
3. The old rbub variable is changed to rsSat for clearity
4. The new interface is tested in test_blackoilfluid with data from
liveoil.DATA and wetgas.DATA
The second input of initBlackoilStateFromDeck that computes surface
volumes based on gas/oil ratio is changed from
BlackoilPropertiesInterface to Props. To avoid duplication with the old
initBlackoilStateFromDeck its name is changed to
initBlackoilSurfvolUsingRS.
Add new function is added that computes saturation from surface volumes
solving z = As for each cell. This function is used to compute an
intial guess to the saturations in initState_impl.hpp.