message: Remove "id" from mine vein data when saving game
  It's no longer used during load, so no need to write it when saving.
diff: @@ -312,7 +312,6 @@ NAS2D::Xml::XmlElement* Mine::serialize(NAS2D::Point<int> location)
  element->linkEndChild(NAS2D::dictionaryToAttributes(
  "vein",
  {{
  - {"id", static_cast<int>(i)},
  {"common_metals", mineVein[OreType::ORE_COMMON_METALS]},
  {"common_minerals", mineVein[OreType::ORE_COMMON_MINERALS]},
  {"rare_metals", mineVein[OreType::ORE_RARE_METALS]},
  