message: Add writing of food level from food producers to StructureManager::serialize
diff: @@ -465,6 +465,13 @@ void StructureManager::serialize(NAS2D::Xml::XmlElement* element)
  structure->linkEndChild(robots);
  }
  + if (it->first->structureClass() == Structure::StructureClass::FoodProduction)
  + {
  + XmlElement* food = new XmlElement("food");
  + food->attribute("level", static_cast<FoodProduction*>(it->first)->foodLevel());
  + structure->linkEndChild(food);
  + }
  +
  structures->linkEndChild(structure);
  }
  