Implemented GameData::Metadata and GameData::MapMetadata

Data/Scripts/013_Overworld/010_PField_RandomDungeons.rb

@@ -555,7 +555,7 @@ end
 Events.onMapCreate += proc { |_sender, e|
   mapID=e[0]
   map=e[1]
-  if pbGetMetadata(mapID,MapMetadata::DUNGEON)
+  if GameData::MapMetadata.get(mapID).random_dungeon
     # this map is a randomly generated dungeon
     dungeon=Dungeon.new(map.width,map.height)
     dungeon.generate