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

@@ -22,11 +22,9 @@ 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) {