message: Have serializeStructure return the generated XmlElement
diff: @@ -26,8 +26,10 @@ namespace
  }
  - void serializeStructure(NAS2D::Xml::XmlElement* structureElement, Structure* structure, Tile* tile)
  + NAS2D::Xml::XmlElement* serializeStructure(Structure* structure, Tile* tile)
  {
  + auto* structureElement = new NAS2D::Xml::XmlElement("structure");
  +
  const auto position = tile->position();
  structureElement->attribute("x", position.x);
  structureElement->attribute("y", position.y);
  @@ -61,8 +63,9 @@ namespace
  structureElement->attribute("pop0", structure->populationAvailable()[0]);
  structureElement->attribute("pop1", structure->populationAvailable()[1]);
  - }
  + return structureElement;
  + }
  }
  @@ -439,8 +442,7 @@ void StructureManager::serialize(NAS2D::Xml::XmlElement* element)
  for (auto& [structure, tile] : mStructureTileTable)
  {
  - auto* structureElement = new NAS2D::Xml::XmlElement("structure");
  - serializeStructure(structureElement, structure, tile);
  + auto* structureElement = serializeStructure(structure, tile);
  if (structure->isFactory())
  {
  