De/Serialization for wavefront object files

Adds to export/import topology as wavefront object files. This enables users to view/edit/use topology inside 3rd party 3D editors

ff/WavefrontSerializer.cpp

@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      ff/WavefronSerializer.cpp
+//! @file      ff/WavefrontSerializer.cpp
 //! @brief     Implements serialization and deserialization for polyhedra.
 //!
 //! @homepage  https://jugit.fz-juelich.de/mlz/libformfactor
@@ -22,18 +22,15 @@ namespace {
 std::ostream& serialize_as_wavefront(std::ostream& out, const ff::Polyhedron* polyhedron)
 {
     out << std::setprecision(10);
-    out << "o 1"
-        << "\n";
+    out << "o 1 \n";
     for (auto vertice : polyhedron->vertices())
-        out << "v"
-            << " " << vertice.x() << " " << vertice.y() << " " << vertice.z() << "\n";
+        out << "v " << vertice.x() << " " << vertice.y() << " " << vertice.z() << "\n";
     out << "usemtl Default\n";
 
     for (auto& poly : polyhedron->topology().faces) {
         if (poly.vertexIndices.size() == 0)
             continue;
-        out << "f"
-            << " ";
+        out << "f ";
         for (size_t i = 0; i < poly.vertexIndices.size(); i++) {
             out << poly.vertexIndices[i] + 1;
             out << (i == poly.vertexIndices.size() - 1 ? "\n" : " ");