message: Use writeResources in StructureManager
diff: #include "Constants.h"
  #include "ProductPool.h"
  +#include "IOHelper.h"
  #include "StructureTranslator.h"
  #include "Things/Structures/Structures.h"
  @@ -413,14 +414,7 @@ void serializeStructure(XmlElement* _ti, Structure* structure, Tile* _t)
  const auto stored = structure->storage();
  if (stored > StorableResources{ 0 })
  {
  - XmlElement* pool = new XmlElement("storage");
  -
  - pool->attribute(constants::SAVE_GAME_RESOURCE_0, stored.resources[0]);
  - pool->attribute(constants::SAVE_GAME_RESOURCE_1, stored.resources[1]);
  - pool->attribute(constants::SAVE_GAME_RESOURCE_2, stored.resources[2]);
  - pool->attribute(constants::SAVE_GAME_RESOURCE_3, stored.resources[3]);
  -
  - _ti->linkEndChild(pool);
  + writeResources(_ti, stored, "storage");
  }
  _ti->attribute("pop0", structure->populationAvailable()[0]);
  