Changes to the props in order to  sync with MRST (Eclipse) 

This PR includes: 
1) Changes in the extrapolation of the unsaturated function values to match them with Eclipse
2) Changes in the way the relperms and capillary pressure tables extrapolates. No the tables extrapolates constantly and not linearly.  
3) The A matrix in the calculation for the surface volume is now computed using an initial guess of the surface volumes based on the RS factor an not only the saturation.