Add interface for wet gas

The pvt interface is extened to handle wet gas
1. A function for rvSat is added to the interface
2. An interface that takes rv and the fluid condition as an input for
the gas properties is added. The old interface without rv and the fluid
condition is kept in the file.
3. The new interface is implemented in BlackoilPropsAd and
BlackoilPropsAdFromDeck.

A simulator that tests wet gas is not yet implemented.
Implementation of live gas
The simulator now handles live gas as well as live oil.
The primary variables are Po,Sw and Rs,Rv or Sg depending on fluid
condition
State 1 Gas only (Undersaturated gas): Po, Sw and Rv
State 2 Gas and oil: Po, Sw and Sg
State 3 Oil only (Undersaturated oil): Po, Sw and Rs

This commit includes:
1. New interfaces for the vapor oil/gas ratios (Rv)
2. Modifications in the equations to handle rvs
3. New definition of ADI variable to handle changing primary variables
4. Modifications in the solution updates to handle changing primary
variable
5. Some changes in the appleyard process to sync with Mrsts livegas
implementation.

NOTE:
The implementation is tested on the liveoil cases SPE1 and a simplified
SPE9 and produces the same results as the old code.
The simulator is not yet able to converge on SPE3 with livegas present.
For SPE3 to converge a more robust well implementation is needed. The
current simulator reproduce the results of Mrst when a similar well
model is used in Mrst as is currently implemented OPM.