Member function dKcdTbyKc in thermo.H is calculated from S and G at Pstd.
Thus dGdT was removed from the thermos.

- Add optional hRef, eRef and Tref as optional.

- Use new thermo to multiphase solver icoReactingMuliPhaseFoam

- Remove hRefConst and eRefConst thermos.

TUT: Updated tutorials