ENH: primitiveMesh: make geometry calculation runtime selectable

This adds a 'geometry' scheme section to the system/fvSchemes:

geometry
{
    type            highAspectRatio;
}

These 'fvGeometryMethod's are used to calculate
- deltaCoeffs
- nonOrthoCoeffs
etc and can even modify the basic face/cellCentres calculation.

applications/utilities/mesh/manipulation/checkMesh/checkMesh.C

@@ -154,6 +154,7 @@ int main(int argc, char *argv[])
         "cellShapes",
         "cellVolume",
         "cellVolumeRatio",
+        "cellAspectRatio",
         "minTetVolume",
         "minPyrVolume",
         "cellRegion",