Cleaned up this worlduid stuff a little.

src/main/java/org/bukkit/craftbukkit/CraftServer.java

@@ -393,7 +393,7 @@ public final class CraftServer implements Server {
             converter.convert(name, new ConvertProgressUpdater(console));
         }
 
-        int dimension = 10 + console.worlds.size();
+        int dimension = Environment.values().length + 1 + console.worlds.size();
         WorldServer internal = new WorldServer(console, new ServerNBTManager(new File("."), name, true), name, dimension, seed, environment, generator);
         internal.worldMaps = console.worlds.get(0).worldMaps;
 
@@ -491,8 +491,7 @@ public final class CraftServer implements Server {
     }
 
     public World getWorld(long uid) {
-        for (String worldName : worlds.keySet()) {
-            org.bukkit.World world = worlds.get(worldName);
+        for (World world : worlds.values()) {
             if (world.getUID() == uid) {
                 return world;
             }