message: Reintroduce writing production resources to savegames
diff: @@ -406,12 +406,13 @@ void serializeStructure(XmlElement* _ti, Structure* structure, Tile* _t)
  _ti->attribute("type", structure->name());
  _ti->attribute("direction", structure->connectorDirection());
  - if (!structure->production().empty())
  + const auto& production = structure->production();
  + if (production > StorableResources{ 0 })
  {
  - //serializeResourcePool(_ti, structure->production(), "production");
  + writeResources(_ti, production, "production");
  }
  - const auto stored = structure->storage();
  + const auto& stored = structure->storage();
  if (stored > StorableResources{ 0 })
  {
  writeResources(_ti, stored, "storage");
  