move n_face of 2D elements to FaceRule

MeshLib/Elements/FaceRule.h

@@ -26,8 +26,8 @@ public:
 	/// Get the number of nodes for face i.
 	static unsigned getNFaceNodes(unsigned /*i*/) { return 2; }
 
-	/// 2D elements have no faces.
-	static unsigned getNFaces() { return 0; }
+	/// Constant: The number of faces
+	static const unsigned n_faces = 0;
 }; /* class */
 
 } /* namespace */

MeshLib/Elements/QuadRule4.h

@@ -49,9 +49,6 @@ public:
 	/// Constant: The FEM type of the element
 	static const CellType cell_type = CellType::QUAD4;
 
-	/// Constant: The number of faces
-	static const unsigned n_faces = 0;
-
 	/// Constant: The number of edges
 	static const unsigned n_edges = 4;
 

MeshLib/Elements/TriRule3.h

@@ -50,9 +50,6 @@ public:
 	/// Constant: The FEM type of the element
 	static const CellType cell_type = CellType::TRI3;
 
-	/// Constant: The number of faces
-	static const unsigned n_faces = 0;
-
 	/// Constant: The number of edges
 	static const unsigned n_edges = 3;