mappedPatchBase: Added patchToPatch as a sampling mode

This mode uses the patchToPatch system (the same one used by NCC) for
coupling two patches. It can be selected for a patch (e.g., in a
blockMeshDict) in the following way:

    fluid_to_solid
    {
        type                mappedWall;
        sampleMode          patchToPatch;
        sampleRegion        solid;
        samplePatch         solid_to_fluid;
        patchToPatchMode    intersection;
        faces
        (
            (0 1 2 3)
            ...
        );
    }

The "patchToPatchMode" can be one of the following:

    "intersection": Values obtained by weighting contributions from
    sampled faces with the intersected area between the faces.
    Equivalent to the nearestPatchFaceAMI sampleMode (which will be
    removed in a future commit).

    "inverseDistance": Values obtained by inverse-distance weighting
    between a small stencil of nearby sampled faces.

    "nearest": Take the value from the nearest sampled face.

    "matching": As nearest, but with checks to ensure that the mapping
    is one-to-one. To be used for mapping between identical patches.

The intention is that patchToPatch will become the only sampleMode, and
the four options above will become the options which determine how
mapping is performed. Cell-to-patch mapping will be transferred into a
separate class as its use cases essentially never intersect with those
of patch-to-patch mapping.

src/functionObjects/field/nearWallFields/nearWallFields.C

@@ -26,7 +26,6 @@ License
 #include "nearWallFields.H"
 #include "wordReList.H"
 #include "findCellParticle.H"
-#include "mappedPatchBase.H"
 #include "OBJstream.H"
 #include "addToRunTimeSelectionTable.H"