Support for the `localBlended` divSchemes?

[TimoLin]

In localBlended scheme, a <variable>BlendingFactor field should be declared as a IOobject in the solver, as defined in:

https://github.com/OpenFOAM/OpenFOAM-7/blob/63349425784a38457964e6470087a2eaac8f0673/src/finiteVolume/interpolation/surfaceInterpolation/schemes/localBlended/localBlended.H#L137-L153

For example, if we set the following divSchemes:

divSchemes
{
    default             none;

    div(phi,U)        Gauss localBlended upwind linear;
...

It will need a UBlendingFactor surfaceScalarField as the blendingFactor in this blended scheme.

[TimoLin]

The UBlend field is not auto-written to the result of new times.

(base) [calc-2nd-localBlend]$ ls processors192/0.02
alphat  C12H26  cellCpuTimes  CO2  H2O  mixfrac  N2  nut  O2  p  phi  PV  Qdot  rho  selectDNN  T  U  UBlend  uniform
(base) [calc-2nd-localBlend]$ ls processors192/0.021
alphat  C12H26  cellCpuTimes  CO2  H2O  Ma  mixfrac  N2  nut  O2  p  phi  PV  Qdot  rho  selectDNN  T  U  uniform