Add comprehensive name function for CellType

src/mesh/CellType.hpp

 #ifndef CELL_TYPE_HPP
 #define  CELL_TYPE_HPP
 
+#include <PastisMacros.hpp>
+#include <string_view>
+
 enum class CellType : unsigned short
 {
   Line = 0,
@@ -14,6 +17,18 @@ enum class CellType : unsigned short
   Hexahedron
 };
 
-
+PASTIS_INLINE
+std::string_view name(const CellType& cell_type)
+{
+  switch (cell_type) {
+    case CellType::Line: return "line";
+    case CellType::Triangle: return "triangle";
+    case CellType::Quadrangle: return "quadrangle";
+    case CellType::Tetrahedron: return "tetrahedron";
+    case CellType::Pyramid: return "pyramid";
+    case CellType::Prism: return "prism";
+    case CellType::Hexahedron: return "hexahedron";
+  }
+}
 
 #endif // CELL_TYPE_HPP