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.

tutorials/mesh/snappyHexMesh/airfoilWithLayers/Allclean

@@ -0,0 +1,9 @@
+#!/bin/sh
+cd "${0%/*}" || exit                                # Run from this directory
+. ${WM_PROJECT_DIR:?}/bin/tools/CleanFunctions      # Tutorial clean functions
+#------------------------------------------------------------------------------
+
+cleanCase0
+rm -rf constant/extendedFeatureEdgeMesh
+
+#------------------------------------------------------------------------------