message: Use raw indexes when saving MineVein data
  This is to make the correspondence more obvious. It also prepares for
  switching MineVein to a StorableResources object, which doesn't
  typically use those enumerated values.
diff: @@ -279,10 +279,10 @@ NAS2D::Xml::XmlElement* Mine::serialize(NAS2D::Point<int> location)
  element->linkEndChild(NAS2D::dictionaryToAttributes(
  "vein",
  {{
  - {ResourceFieldNames[0], mineVein[OreType::ORE_COMMON_METALS]},
  - {ResourceFieldNames[1], mineVein[OreType::ORE_COMMON_MINERALS]},
  - {ResourceFieldNames[2], mineVein[OreType::ORE_RARE_METALS]},
  - {ResourceFieldNames[3], mineVein[OreType::ORE_RARE_MINERALS]},
  + {ResourceFieldNames[0], mineVein[0]},
  + {ResourceFieldNames[1], mineVein[1]},
  + {ResourceFieldNames[2], mineVein[2]},
  + {ResourceFieldNames[3], mineVein[3]},
  }}
  ));
  }
  